CN115146370A - Benchmarking correction method and comfort judgment method for automobile transmission system model - Google Patents

Benchmarking correction method and comfort judgment method for automobile transmission system model Download PDF

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CN115146370A
CN115146370A CN202210220458.2A CN202210220458A CN115146370A CN 115146370 A CN115146370 A CN 115146370A CN 202210220458 A CN202210220458 A CN 202210220458A CN 115146370 A CN115146370 A CN 115146370A
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杨义勇
李亚飞
赵永涛
王翔宇
李亮
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China University of Geosciences Beijing
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Abstract

The application relates to a benchmarking correction method and a comfort judgment method for an automobile transmission system model, wherein the benchmarking correction method comprises the following steps: carrying out linear acceleration test on an actual vehicle to obtain a first vehicle speed time variation relation, a first engine torque time variation relation and a first transmission gear time variation relation; establishing an initial automobile transmission system model; determining the optimized value of each coefficient in the initial automobile transmission system model by using a genetic algorithm; and substituting the obtained optimized values of the coefficients in the parameter population into the initial automobile transmission system model to obtain the automobile transmission system model after the benchmarking correction. The automobile transmission system model can be obtained according to the acceleration test result of the actual vehicle, so that the automobile linear acceleration and deceleration test can be simulated by directly utilizing the automobile transmission system model after the calibration correction in the follow-up process without carrying out related tests on the actual vehicle.

Description

Benchmarking correction method and comfort judgment method for automobile transmission system model
Technical Field
The invention belongs to the field of automobile transmission system models, and particularly relates to a benchmarking correction method and a comfort judgment method for an automobile transmission system model.
Background
In the development process of an automatic transmission automobile, a gear shifting logic matched with the automobile needs to be set. In order to adjust a proper shift logic, the conventional method includes setting different shift logics for an actual vehicle, and repeatedly performing linear acceleration and deceleration tests on the actual vehicle according to the different shift logics to obtain related data, so that the shift logic is adjusted, and finally, the shift logic meeting comfort is obtained.
In the process, the driver is required to repeatedly drive the automobile for testing, so that the driver has great fatigue feeling, the operation of the driver on the automobile is possibly influenced, and the accident danger is generated; the test time for each driving is longer, so that the time for adjusting the gear shifting logic is prolonged, and the development cycle of the automatic transmission automobile is also prolonged; in addition, in the case of a great mismatch in shift logic, driving an actual vehicle under test can cause great damage to the engine and various transmission components of the automobile, thereby incurring additional maintenance costs.
Disclosure of Invention
In view of the above, the invention provides a benchmarking correction method for an automobile transmission system model and a comfort judgment method, which can obtain the benchmarking corrected automobile transmission system model corresponding to an actual vehicle according to an acceleration test result of the actual vehicle, so that the automobile linear acceleration and deceleration test can be directly simulated by using the benchmarking corrected automobile transmission system model subsequently without performing a related test on the actual vehicle, thereby improving the safety of a process of obtaining related data, reducing the time for adjusting and correcting a gear shifting logic, and avoiding additional maintenance cost generated by the actual vehicle test.
The technical scheme adopted by the invention is as follows:
a benchmarking correction method of an automobile transmission system model based on a genetic algorithm is used for evaluating whether automobile gear shifting logic accords with comfort; the method comprises the following steps:
s100, carrying out linear acceleration test on an actual vehicle, and acquiring a first vehicle speed, a first torque output by an engine and a first gear of a transmission of the actual vehicle in the process to obtain a time-varying relation of the first vehicle speed, a time-varying relation of the first engine torque and a time-varying relation of the first transmission gear;
s200, establishing an initial automobile transmission system model, wherein the initial automobile transmission system model comprises a corresponding relation between a longitudinal force of a driving wheel, a longitudinal force of a driven wheel and a vehicle speed; the longitudinal force of the driving wheel is determined according to the torque of an engine, the gear of a transmission, the transmission ratio corresponding to the gear of the transmission, the transmission efficiency corresponding to the gear of the transmission, the transmission ratio of a speed reducer and the transmission efficiency of the speed reducer; said driven wheel longitudinal force F xf Comprises the following steps:
F xf ＝Dsin(Carctan(Bx-E(Bx-arctan(Bx))))；
b is a rigidity factor coefficient, C is a curve shape factor coefficient, D is a peak factor coefficient, E is a curve curvature factor coefficient, and x represents the slip ratio of the driven wheel;
s300, determining an optimized value of each coefficient in an initial automobile transmission system model by using a genetic algorithm; the parameter population in the genetic algorithm comprises a plurality of groups of parameter groups, wherein each group of parameter comprises a coefficient B, C, D, E; the fitness function and the termination condition are determined according to the relation that the simulated vehicle speed output by the initial automobile transmission system model changes along with time and the first vehicle speed changes along with time as a target when the first engine torque changes along with time and the first transmission gear changes along with time are used as input;
and S400, substituting the optimized values of the coefficients in the parameter population obtained in the step S300 into the initial automobile transmission system model to obtain the automobile transmission system model after the benchmarking is corrected.
Preferably, in step S200, the initial vehicle transmission system model is:
Figure BDA0003536994810000021
where n is the number of wheels on the front and rear axles, i (T) is the gear i of the transmission at time T, g (i (T)) is the gear ratio of the transmission in gear i (T), τ (i (T)) is the transmission efficiency of the transmission in gear i (T), and T (T) is the transmission efficiency of the transmission in gear i (T) e (t) is the output torque of the engine at time t, g f Is the gear ratio of the speed reducer, eta f For the transmission efficiency of the speed reducer, r w Is the radius of the driving wheel, C d Is the wind resistance coefficient, rho is the air density, A is the windward area of the automobile, V (t) is the simulated speed at the moment t in the automobile transmission system model, V w Is the wind speed, m is the mass of the car,
Figure BDA0003536994810000022
the acceleration is the simulated acceleration at the moment t in the automobile transmission system model, g is the gravity acceleration, and beta is the ramp angle.
Preferably, in step S300, each parameter set further includes a coefficient C d 。
Preferably, in step S300, each coefficient B, C, D, E and C in the parameter population d The value range of (A) is as follows,
5≤B≤50，1≤C≤10，1≤D≤10，0.5≤E≤5，0.2≤C d ≤0.4。
preferably, in step S300, the fitness function is
Figure BDA0003536994810000031
Wherein y is the simulation running time, S y Is the total number of times of sampling in the y-th simulation, V (t) y And V (t)' is the actual vehicle speed at the t moment in the time variation relation of the first vehicle speed.
Preferably, the termination condition is that MSE (y) is less than a predetermined value, the predetermined value being 0 to 0.25.
Preferably, the step S300 includes the steps of:
s310, randomly generating an initial parameter population; the initial parameter population comprises N groups of parameter groups, wherein N is greater than or equal to 20 and less than or equal to 50;
s320, respectively taking each parameter group as an individual, taking a first engine torque time-varying relation and a first transmission gear time-varying relation as input to simulate an initial automobile transmission system model, obtaining a simulated vehicle speed time-varying relation of each individual, and respectively calculating a fitness corresponding to each individual, wherein the fitness is a numerical value obtained according to a fitness function;
s330, judging whether an individual meeting a termination condition exists, if so, executing a step S350; otherwise, executing step S340;
s340, selecting a preset number of individuals with the lowest fitness as parents, performing cross and/or variation to obtain a new parameter population, and returning to the step S320;
s350, outputting the individuals meeting the termination condition as a better parameter group, and determining the optimized values of all the coefficients in the initial automobile transmission system model according to the better parameter group.
Preferably, in step S350, when there are a plurality of individuals satisfying the termination condition, the individual with the minimum fitness is used as the optimized value of each coefficient.
The invention also provides a method for judging whether the gear shifting logic meets the comfort by using the automobile transmission system model, which comprises the following steps:
s10, obtaining an automobile transmission system model after benchmarking correction by using the benchmarking correction method;
s20, acquiring a preset time-varying relation of the transmission gear and a plurality of corresponding second engine torques; wherein the predetermined transmission gear shift is a function of engine torque and vehicle speed over time;
s30, respectively taking the time-varying relations of the second engine torques and the time-varying relations of the preset transmission gears as the input of the corrected automobile transmission system model to obtain a plurality of second vehicle speed time-varying relations;
s40, obtaining a plurality of second jerk time-varying relations according to the plurality of second vehicle speed time-varying relations;
and S50, judging whether the jerk in the second jerk time-varying relations is in a set comfort interval range or not, obtaining the proportion of the number of the second jerk time-varying relations which are always in the set comfort interval range and the total number of the second jerk time-varying relations obtained in the step S40, and if the proportion is not less than the preset proportion, enabling the preset transmission gear time-varying relation to meet the comfort requirement.
Preferably, the step S50 further includes:
if the ratio is smaller than the preset ratio, the change relation of the preset transmission gear with time does not meet the comfort requirement, the change relation of the preset transmission gear with time is adjusted, and then the step S20 is carried out.
The invention has the beneficial effects that:
the method comprises the steps of firstly establishing an initial automobile transmission system model, setting an initial parameter population, taking a first engine torque time-varying relation and a first transmission gear time-varying relation obtained by an actual vehicle linear acceleration test as input of the model, taking the first vehicle speed time-varying relation obtained by the actual vehicle test as an output target of the model, carrying out standard correction on the initial automobile transmission system model, establishing a moderate function according to the simulated vehicle speed time-varying relation and the target output by the initial automobile transmission system model each time in the process of standard correction, adjusting each coefficient of the initial automobile transmission system model by using a genetic algorithm, and repeatedly simulating to obtain a corresponding simulated vehicle speed time-varying relation until the simulated vehicle speed time-varying relation obtained by the simulation of the initial automobile transmission model is close to the first vehicle speed time-varying relation, thereby obtaining the automobile transmission system model after the standard correction. The obtained automobile transmission system model can simulate the running condition of an actual vehicle under the time-varying relation of other engine torques and/or the time-varying relation (gear shifting logic) of the preset transmission gears, so that a driver does not need to carry out an actual vehicle driving test in the gear shifting logic test of the vehicle on the transmission, the test of different gear shifting logics on the actual vehicle is avoided, and the accident danger generated in the research and development process is reduced; the automobile transmission system model after the benchmarking correction is adopted, so that the time for adjusting the gear shifting logic can be shortened compared with the actual automobile test, and the development period of the automatic transmission automobile is further shortened; the engine and each transmission component of the automobile can be prevented from being greatly damaged in the real-vehicle test under the condition that the gear shifting logic poles are not matched, and the research and development cost is further reduced.
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The above and other objects, features and advantages of the present application will become more apparent from the following description of embodiments thereof with reference to the accompanying drawings, in which:
FIG. 1 is a block flow diagram of a benchmarking method for a genetic algorithm based model of an automotive transmission system in accordance with the present invention;
fig. 2 is a detailed flowchart of step S300;
FIG. 3 is a block flow diagram of a method of determining whether shift logic meets comfort using a model of a vehicle powertrain, in accordance with the present invention.
Detailed Description
The present application is described below based on examples, but the present application is not limited to only these examples. In the following detailed description of the present application, certain specific details are set forth in order to avoid obscuring the nature of the present application, well-known methods, procedures, and components have not been described in detail.
Further, those of ordinary skill in the art will appreciate that the drawings provided herein are for illustrative purposes and are not necessarily drawn to scale.
Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, what is meant is "including, but not limited to".
In the description of the present application, it is to be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In addition, in the description of the present application, the meaning of "a plurality" is two or more unless otherwise specified.
Referring to fig. 1, the present invention relates to a calibration correction method for a vehicle transmission system model based on a genetic algorithm, the vehicle transmission system model being used for evaluating whether a vehicle shift logic is comfortable or not; the method comprises the following steps:
s100, carrying out linear acceleration test on an actual vehicle, and acquiring a first vehicle speed, a first torque output by an engine and a first gear of a transmission of the actual vehicle in the process to obtain a time-varying relation of the first vehicle speed, a time-varying relation of the first engine torque and a time-varying relation of the first transmission gear;
s200, establishing an initial automobile transmission system model, wherein the initial automobile transmission system model comprises a corresponding relation between a longitudinal force of a driving wheel, a longitudinal force of a driven wheel and a speed; the longitudinal force of the driving wheel is determined according to engine torque, transmission gears, transmission ratios corresponding to the transmission gears, transmission efficiencies corresponding to the transmission gears, transmission ratios of the speed reducer and transmission efficiencies of the speed reducer; said driven wheel longitudinal force F xf Comprises the following steps:
F xf ＝Dsin(Carctan(Bx-E(Bx-arctan(Bx))))；
wherein, B is a rigidity factor coefficient, C is a curve shape factor coefficient, D is a peak factor coefficient, E is a curve curvature factor coefficient, and x represents the slip ratio of the driven wheel;
s300, determining an optimized value of each coefficient in an initial automobile transmission system model by using a genetic algorithm; the parameter population in the genetic algorithm comprises a plurality of groups of parameter groups, wherein each group of parameter comprises a coefficient B, C, D, E; the fitness function and the termination condition are determined according to the relation that the simulated vehicle speed output by the initial automobile transmission system model changes along with time and the first vehicle speed changes along with time as a target when the first engine torque changes along with time and the first transmission gear changes along with time are used as input;
and S400, substituting the optimized values of the coefficients in the parameter population obtained in the step S300 into the initial automobile transmission system model to obtain the automobile transmission system model after the benchmarking is corrected.
In step S100, the "actual vehicle" is a vehicle that can be actually driven, the actual vehicle is an automatic transmission vehicle, and the actual vehicle is a two-wheel drive vehicle, such as a front-wheel drive vehicle or a rear-wheel drive vehicle, and if the actual vehicle is a front-wheel drive vehicle, two front wheels are driving wheels and two rear wheels are driven wheels; for example, a rear wheel drive automobile, two rear wheels are driving wheels, and two front wheels are driven wheels. The shape of the actual vehicle, the corresponding parameters of the hardware such as the engine, the gearbox, the reducer, the tire, the transmission shaft and the like are fixed. The "straight line acceleration test" is a process in which the driver drives the actual vehicle to travel along a straight line acceleration, for example, a process in which the driver drives the actual vehicle to accelerate from 0km/h to a target vehicle speed along a straight line, where the target vehicle speed may be 30km/h, 60km/h, 90km/h, or 120km/h, etc.; in addition, during the straight line acceleration test of the actual vehicle, the driver can not actively brake the actual vehicle. The actual vehicle is provided with related sensors, and can acquire the engine torque (corresponding to the first torque), the transmission gear (corresponding to the first gear) and the actual vehicle speed (corresponding to the first vehicle speed) of the actual vehicle in real time in the linear acceleration test process, so as to obtain a first engine torque variation relationship with time, a first transmission gear variation relationship with time and a first vehicle speed variation relationship with time, wherein the first engine torque variation relationship with time describes the variation relationship of the output torque of the engine with time, and in one embodiment, the variation curve of the output torque of the engine with time; "first transmission gear versus time" describes transmission gear versus time, in one embodiment a transmission gear versus time square wave plot; "first vehicle speed versus time" describes the actual vehicle speed versus time, and in one embodiment, is a plot of actual vehicle speed versus time.
The "linear acceleration test" process in the preceding paragraph does not mean that the vehicle speed is always in a raised state in the process, but includes the case that the vehicle speed is kept unchanged and the vehicle speed is reduced during the running of the vehicle, but the vehicle speed reduction in the process refers to the reduction of the vehicle speed under the condition that the driver does not actively brake, such as the vehicle is in a climbing state.
In step S200, the initial automobile transmission model can be used to simulate a time variation relationship of a simulated vehicle speed during straight-line driving of the automobile, and specifically, the initial automobile transmission model can describe a corresponding relationship between a driving wheel longitudinal force, a driven wheel longitudinal force and a vehicle speed, where the driving wheel longitudinal force at time t can be represented as F xr (t) driven wheel longitudinal force F xf Longitudinal force F of driven wheel xf Can be expressed as:
F xf ＝Dsin(Carctan(Bx-E(Bx-arctan(Bx))))……………………(1)
wherein, B is a rigidity factor coefficient, C is a curve shape factor coefficient, D is a peak factor coefficient, E is a curve curvature factor coefficient, and x represents the slip ratio of the driven wheel.
In the formula (1), the specific value of x can be obtained by an internal packaging program of the simulation software MATLAB, wherein in the packaging program, x is used as a variable which is related to the total longitudinal force (i.e. F in the following) applied to the automobile x (t)), the vertical load to which the driven wheel is subjected, and the adhesion coefficient of the road surface (which can be obtained by detection and is constant) are correlated, and therefore, can be determined from the total longitudinal force in the model and the input adhesion coefficient.
In the initial automobile transmission system model, the longitudinal force of the driving wheel is determined according to the torque of the engine, the gear position of the speed changer, the transmission ratio corresponding to the gear position of the speed changer, the transmission efficiency corresponding to the gear position of the speed changer, the transmission ratio of the speed reducer and the transmission efficiency of the speed reducer. In an actual vehicle, an output shaft of an engine is in transmission connection with an input shaft of a transmission, and an output shaft of the transmission is in transmission connection with an input shaft of a speed reducer to reduceThe output shaft of the speed changer is in transmission connection with the driving wheel, the speed reducer has fixed transmission ratio and transmission efficiency, each gear of the speed changer also has fixed transmission ratio and transmission efficiency, and therefore the longitudinal force F of the driving wheel can be determined through the torque of the engine and the gear of the speed changer xr (t)。
In step S300, in the initial automobile transmission system model, the coefficients B, C, D, E are the coefficients to be optimized in the model, and the present invention determines optimized coefficient values by simulating the initial automobile transmission system model based on a genetic algorithm, and generates a plurality of sets of parameter sets each including a specific value of the coefficient B, C, D, E, that is, equivalent to an individual described below, in each simulation, thereby obtaining the output of the plurality of sets of initial automobile transmission system models. Specifically, in the whole simulation process, the input of the initial automobile transmission system model is the same, the input is the first engine torque time-varying relation and the first transmission gear time-varying relation, only the specific numerical values of the coefficients B, C, D, E of different groups in each simulation and the same simulation are different, therefore, the output of different groups in each simulation and the same simulation is also different, and the output is the simulated vehicle speed time-varying relation corresponding to the input. If the fitness does not reach the termination condition, generating a plurality of groups of parameter groups as a new parameter group in the next simulation according to a genetic algorithm, and recalculating the fitness corresponding to each group of parameter groups until the fitness meeting the termination condition appears. The fitness function is related to the time-varying relation of the output simulated vehicle speed and the time-varying relation of the first vehicle speed serving as the target, and the time-varying relation of the first vehicle speed is a fixed relation and is a function of the time-varying relation of the output simulated vehicle speed; the termination condition may be related to the function value of the fitness function, for example, if the set function value needs to satisfy a predetermined condition.
In step S400, the optimized values B, C, D, E obtained in step S300 are substituted into the initial automobile transmission system model to obtain the benchmarked automobile transmission system model, and in the later period, the benchmarked automobile transmission system model can be used to simulate the time-varying relationship of other engine torques and the time-varying relationship of other transmission gears (which may be the following shift logic) as input to obtain the simulated time-varying relationship of vehicle speed, so that the driver is not required to obtain relevant test data (the simulated time-varying relationship of vehicle speed) by driving an actual vehicle every time the time-varying relationship of engine torques and the change logic of transmission gears are adjusted, thereby avoiding the test of different shift logics on the actual vehicle and reducing the risk of accidents in the research and development process; the automobile transmission system model after the benchmarking correction is adopted, so that the time for adjusting the gear shifting logic can be shortened compared with the actual automobile test, and the development period of the automatic transmission automobile is further shortened; the engine and each transmission component of the automobile can be prevented from being greatly damaged in the real-vehicle test under the condition that the gear shifting logic poles are not matched, and the research and development cost is further reduced.
Specifically, in step S200, the initial vehicle driveline model may be represented by the following dynamic model:
Figure BDA0003536994810000091
F x (t)＝n(F xf +F xr (t))………………………………(3)
Figure BDA0003536994810000092
wherein: m is the mass of the automobile,
Figure BDA0003536994810000093
for the simulated acceleration at time t, F, in a model of the vehicle driveline x (t) is the total longitudinal force to which the vehicle is subjected at time t, F d (t) air resistance at time t, g is gravitational acceleration, β is ramp angle, n is the number of wheels on the front and rear axles, F xf For driven wheel longitudinal forces, F xr (t) longitudinal force of the driving wheel at time t, C d Is the wind resistance coefficient, rho is the air density, A is the windward area of the automobile, V (t) is the simulated speed at the moment t in the automobile transmission system model, V w Is the wind speed.
The formula (2) is obtained according to Newton's second law, and describes the relationship between the longitudinal force applied to the automobile model and the acceleration of the automobile model, wherein g is the gravity acceleration and belongs to a constant, and the numerical value of g is unchanged in the initial automobile transmission system model and the automobile transmission system model after calibration correction; in the initial automobile transmission system model, beta is the same as the ramp angle of the linear acceleration test in the step S100, and in the automobile transmission system model after the calibration correction, beta can be manually set according to actual requirements; in the initial vehicle transmission system model, the mass m is the same as the mass of the actual vehicle in the linear acceleration test in step S100, and in the vehicle transmission system model after the calibration correction, since the number of the drivers and passengers on the vehicle to be simulated changes, the value of the mass m changes from the mass in the linear acceleration test of the actual vehicle, the mass m can be set manually according to the state of the vehicle to be simulated.
Equation (3) expresses the relationship between the total longitudinal force experienced by the automobile model and the longitudinal force of the driving wheel and the longitudinal force of the driven wheel, and n is 2 in general.
Equation (4) is an expression of air resistance. In the initial model of the vehicle drive train, the air density ρ and the wind speed V w The same as the related data in step S100; in the corrected automobile transmission system model, the air density rho and the wind speed V w The artificial setting can be carried out according to the actual simulation condition. The frontal area A of the automobile and the frontal area of the actual vehicle are obtained by measuring the actual vehicle, and the frontal area A of the automobile is a constant. Coefficient of wind resistance C d Can enter through an actual vehicleMeasured by a line test (wind tunnel test), C d Is a constant.
Integrating the equations (2), (3) and (4) to obtain:
Figure BDA0003536994810000101
substituting equation (1) into equation (5) yields:
Figure BDA0003536994810000102
Figure BDA0003536994810000103
specifically, the initial vehicle drive system model in step S200 includes an engine model, a transmission model, and a reduction gear model, and in the present invention, the longitudinal force F of the drive wheel at time t is represented by the engine model, the transmission model, and the reduction gear model xr (t) of (d). Wherein:
the engine model is expressed as:
T e (t)…………………………………………(7)
T e (t) is the output torque of the engine at time t.
The transmission model is represented as:
T t (t)＝T t (g,τ,i)＝g(i(t))·τ(i(t))·T e (t)………………(8)
wherein, T t (t) is the transmission output torque at time t, i (t) is the gear position i of the transmission at time t, g (i (t)) is the gear ratio of the transmission in gear position i (t), and τ (i (t)) is the transmission efficiency of the transmission in gear position i (t).
The transmission of the vehicle is an AT transmission or a DCT transmission, so that the transmission has several fixed gears, each gear has a corresponding fixed transmission ratio and transmission efficiency, the transmission ratio and the transmission efficiency of each gear can be obtained by collecting the transmission ratio and the transmission efficiency of the transmission under the corresponding gear, and can also be obtained by referring to the parameters of the transmission (such as a nameplate or a specification of a speed reducer), and therefore, the transmission ratio and the transmission efficiency of each gear of the transmission are constant in an initial automobile transmission system model and an automobile transmission system model after the benchmarking is corrected.
The retarder model is represented as:
T f (t)＝T t (t)·g f ·η f …………………………(9)
wherein, T f (t) is the output torque of the reducer at time t, g f Is the gear ratio of the speed reducer, eta f The transmission efficiency of the speed reducer is improved.
The reducer having a fixed reducer drive ratio g f And fixed reduction gear transmission efficiency eta f The speed reducer transmission ratio g can be acquired during the running of the speed reducer on the actual vehicle or obtained from the parameters of the speed reducer itself (such as from the name plate or specification of the speed reducer), so that the speed reducer transmission ratio g is obtained in the initial automobile transmission system model and the automobile transmission system model after the calibration correction f And fixed reduction gear transmission efficiency eta f Are all constants.
The output shaft of the speed reducer is in transmission connection with the driving wheel, and the output torque of the speed reducer directly acts on the driving wheel, so that the longitudinal force of the driving wheel changes along with time and is represented as follows:
Figure BDA0003536994810000111
wherein r is w Is the radius of the driving wheel.
Radius of driving wheel r w Obtained by measuring the radius of the drive wheel of the actual vehicle, r w Is constant (i.e. r in the initial and corrected model of the vehicle driveline w Value of (2) unchanged).
The equations (7), (8), (9) and (10) are integrated to obtain:
Figure BDA0003536994810000112
in the formula (11), g f 、η f And r w Are all known constants and thus can be input by T e (t) and i (t) to give F xr (t), and thus the primary pulley longitudinal force may be determined in step S200 based on the engine torque, the transmission gear, the gear ratio corresponding to the transmission gear, and the gear efficiency corresponding to the transmission gear, and the gear ratio of the retarder and the gear efficiency of the retarder.
Substituting equation (11) into equation (6) results in the final initial vehicle driveline model:
Figure BDA0003536994810000113
wherein, the relationship between the acceleration and the vehicle speed can be expressed as:
Figure BDA0003536994810000114
wherein, V 0 The vehicle speed at time 0, i.e., the initial speed of the vehicle.
In step S100, if the linear acceleration test is a process of accelerating from 0km/h to a target vehicle speed, V is in an initial automobile transmission system model 0 Is 0km/h. The initial speed of the actual vehicle is not 0km/h as in the straight line acceleration test, and V is in the initial automobile transmission system model 0 The initial speed of the actual vehicle may be obtained by measurement and set in an initial vehicle drive train model.
In the calibrated model of the vehicle drive train, V 0 The numerical value is preset, and the operator can set the numerical value autonomously according to the condition needing to be simulated.
In the initial driveline model, equations (12) and (13), B, C, D, E is the coefficient to be determined, T e (t), i (t), V (t) and
Figure BDA0003536994810000121
the variation with time is variable and other quantities are determined before simulation, and in step S300, by simulation based on genetic algorithm, coefficients B, C, D and E are determined each time simulation is performed, by T e (t) inputting the first engine torque time-varying relation, i (t) inputting the first transmission gear time-varying relation, thereby obtaining the simulated vehicle speed time-varying relation (namely a graph of the simulated vehicle speed from the time 0 to the ending time point).
Similarly, in the vehicle transmission system model after calibration correction, the coefficients B, C, D and E are both determined, and the operator inputs the pretested T e (T) and i (T) (where i (T) may be according to the shift logic and T below e (t) determining), and simulating the time variation relationship of the simulated vehicle speed.
Although coefficient C d Can be obtained by a wind tunnel test, but because the cost required by the wind tunnel test is too high, in a preferred embodiment of the invention, the coefficient C d Also included in the coefficients of the parameter set, i.e. in step S300, the parameter set further includes a coefficient C d And then obtaining a corresponding optimized value through a simulation process based on a genetic algorithm, wherein in step S300, the parameter set simultaneously comprises coefficients B, C, D, E and C d (ii) a In step S400, B, C, D, E and C are combined d And substituting the optimized value into the initial automobile transmission system model to obtain the automobile transmission system model after the calibration correction.
Preferably, in step S300, each coefficient B, C, D, E and C in the parameter population d The value range of B is more than or equal to 5 and less than or equal to 50,1 and less than or equal to 10,1 and less than or equal to D and less than or equal to 10,0.5 and less than or equal to E and less than or equal to 5,0.2 and less than or equal to C d ≤0.4。
The value range of each coefficient is limited, so that the algebra of the genetic algorithm can be reduced, and the time for obtaining the automobile transmission system model after the benchmarking correction is shortened.
Preferably, in step S300, the fitness function is
Figure BDA0003536994810000122
Wherein y is the simulation run time, S y Is the total number of times of sampling in the y-th simulation, V (t) y And V (t)' is the actual vehicle speed at the t moment in the time variation relation of the first vehicle speed.
The first engine torque at the time point in the time-varying relation of the first engine torque is taken as T e (t) the first transmission gear at the corresponding time point in the time-varying relationship of the first transmission gear is input as i (t) to the initial model of the vehicle driveline (B, C, D, E and C) d Is determined by the corresponding parameter set), and thus the y-th simulated vehicle speed is output through the initial vehicle transmission system model according to the time variation relationship, wherein the simulated vehicle speed at the time t is V (t) y 。
The first vehicle speed V' (t) at time t in the first vehicle speed time-varying relation has been acquired in step S100.
The fitness function can express the discrete degree of the time-varying relation of the y-th simulated vehicle speed and the time-varying relation of the first vehicle speed, and is realized by using a variance formula, namely, the lower the fitness value calculated by the fitness function is, the closer the time-varying relation of the y-th simulated vehicle speed to the time-varying relation of the first vehicle speed is, the closer the initial automobile transmission system model for obtaining the time-varying relation of the y-th simulated vehicle speed to an actual vehicle is.
Of course, the fitness function may also be expressed as
Figure BDA0003536994810000131
Preferably, the termination condition is that MSE (y) is less than a predetermined value, the predetermined value being 0 to 0.25. The smaller the preset value is, the closer the finally obtained benchmarked modified automobile transmission system model is to the actual vehicle, but the smaller the preset value is (the preset value is 0 or infinitely close to 0), the population algebra of the genetic algorithm is increased (specifically, see below), and the longer the time for obtaining the benchmarked modified automobile transmission system model is. Therefore, the preset value should be set reasonably, and in the present invention, the preset value is preferably 0.03, 0.05, 0.07, 0.09, 0.1, 0.15, 0.2 or 0.25. Therefore, the time for obtaining the benchmarking corrected automobile transmission system model can be shortened while the benchmarking corrected automobile transmission system model is close to an actual vehicle.
Of course, the termination condition is that MSE (y) is less than a predetermined value, which is 0 to 0.3. For example, 0.26, 0.27, 0.28, 0.29, or 0.3.
Preferably, referring to fig. 2, the step S300 includes the steps of:
s310, randomly generating an initial parameter population; the initial parameter population comprises N groups of parameter groups, wherein N is greater than or equal to 20 and less than or equal to 50;
s320, respectively taking each parameter group as an individual, taking a first engine torque time-varying relation and a first transmission gear time-varying relation as input to simulate an initial automobile transmission system model, obtaining a simulated vehicle speed time-varying relation of each individual, and respectively calculating a fitness corresponding to each individual, wherein the fitness is a numerical value obtained according to a fitness function;
s330, judging whether an individual meeting the termination condition exists, if so, executing a step S350; otherwise, executing step S340;
s340, selecting a preset number of individuals with the lowest fitness as parents, performing cross and/or variation to obtain a new parameter population, and returning to the step S320;
and S350, outputting the individuals meeting the termination condition as a better parameter group, and determining the optimized value of each coefficient in the initial automobile transmission system model according to the better parameter group.
In step S310, the randomly generated initial parameter population P0 includes N sets of parameter sets, that is, the initial parameter population P0 includes N individuals, and each parameter set includes coefficients B, C, D, E and C d Wherein each coefficient isThe specific values of (a) are all randomly selected within the corresponding value range.
In addition, e.g. coefficient C d The parameter set comprises specific values of coefficients B, C, D and E.
Each parameter set in the initial parameter population P0 is different, that is, in the initial parameter population P0, at least one of the coefficients in any two parameter sets has a different value.
The number of initial parameter groups P0 is 20-50, for example, 20, 25, 27, 30, 32, 35, 38, 40, 42, 45, 47, 50, etc., and a suitable number of samples are provided, and too few parameter groups increase the population generation number of the genetic algorithm, thereby slowing down the time for obtaining the standard modified vehicle transmission system model, while too many parameter groups increase the time for performing the simulation on the vehicle transmission system model of each generation and slow down the time for obtaining the standard modified vehicle transmission system model.
In step S320, each parameter group of the initial parameter population P0 is respectively used as an individual, so that individuals having the same number as the parameter groups can be obtained, the numerical value of each coefficient in each individual is respectively assigned to the initial automobile transmission system model, an initial automobile transmission system model corresponding to the individual one to one is obtained, and the first engine torque at the corresponding time point in the time-varying relation of the first engine torque is used as T e (t) inputting the first transmission gear at the corresponding time point in the time-varying relation of the first transmission gears as i (t) into the initial automobile transmission system models for simulation, so that each initial automobile transmission system model can output a simulated vehicle speed time-varying relation, and because the individuals have differences, the simulated vehicle speed time-varying relation corresponding to the individuals also has differences, and respectively calculating the fitness of the simulated vehicle speed time-varying relation corresponding to each individual and the first vehicle speed time-varying relation through the fitness function.
In step S330, the fitness of each individual is compared with the termination condition, so as to determine whether there is an individual satisfying the termination condition.
For example, the termination condition is set to be MSE (y) less than 0.15, and for a single individual, if the fitness of the individual is less than 0.15, the individual satisfies the termination condition; otherwise, if the fitness of the individual is more than or equal to 0.15, the individual does not meet the termination condition.
In step S330, if there are individuals satisfying the termination condition, then step S350 is executed, where "there are individuals satisfying the termination condition" means that at least one of the individuals satisfying the termination condition is the individual satisfying the termination condition; if there are no individuals satisfying the termination condition, step S340 is executed, and "no individuals satisfying the termination condition" means that all individuals do not satisfy the termination condition.
In step S340, because no individual meeting the termination condition is obtained in step S330, a good individual is selected according to the fitness of each individual, where the good individual can be evaluated through the fitness of each individual, that is, an individual with low fitness is better than an individual with high fitness, so that a preset number of individuals with the highest fitness can be selected according to the fitness of each individual, where the preset number is preferably 5-10, and in actual application, the preset number may be set manually according to requirements, and if the preset number is 5, 5 individuals with the lowest fitness are selected, and the 5 individuals are used as parents to be crossed and/or mutated to obtain a new parameter population.
In addition, the specific values of the coefficients in the parameter group in the new parameter population are still limited by the foregoing value range.
For example, 20 sets of parameter groups are in the initial parameter population P0, and all the formed 20 individuals do not satisfy the termination condition, so in step S340, according to the fitness of the 20 individuals, 5 individuals with the lowest fitness are screened out as parents to perform intersection and/or variation, so as to obtain a new-generation parameter population P1 (new parameter population), then the fitness of each individual of the new-generation parameter population P1 is respectively calculated in step S320, and in step S330, it is determined whether there is an individual satisfying the termination condition, such as an individual still not satisfying the termination condition, and then a new-generation parameter population P2 (new parameter population) is generated in step S340, and the above process is repeated until an individual satisfying the termination condition is obtained, and then the process is terminated.
In step S340, the number of groups of parameter groups in the new parameter population is preferably equal to the number of groups of parameter groups in the initial parameter population, or the number of groups of parameter groups in the new parameter population may not be equal to the number of groups of parameter groups in the initial parameter population, but the number of groups of parameter groups in the new parameter population is still controlled within the range of 20-50.
When the individuals satisfying the termination condition are present in step S330, step S350 is executed. In step S350, it is possible to directly output an individual satisfying the termination condition, and the parameter group corresponding to the individual satisfying the termination condition is the preferred parameter group. The specific value of each coefficient in the better parameter group is the optimized value of each coefficient, so that the calibrated and corrected automobile transmission system model can be conveniently obtained in the subsequent step S400.
However, in some cases, when the number of individuals satisfying the termination condition is plural, the individual having the smallest fitness is used as the optimum value of each coefficient.
Referring to fig. 3, the present invention further provides a method for determining whether shift logic satisfies comfort using a vehicle driveline model, comprising the steps of:
s10, obtaining an automobile transmission system model after calibration correction by using the calibration correction method;
s20, acquiring a preset time-varying relation of the transmission gear and a plurality of corresponding second engine torques; wherein the predetermined transmission gear shift is a function of engine torque and vehicle speed over time;
s30, respectively taking the time-varying relations of the second engine torques and the time-varying relations of the preset transmission gears as the input of the corrected automobile transmission system model to obtain a plurality of second vehicle speed time-varying relations;
s40, obtaining a plurality of second jerk time-varying relations according to the plurality of second vehicle speed time-varying relations;
and S50, judging whether the jerk in the second jerk time-varying relations is in a set comfort interval range or not, obtaining the proportion of the number of the second jerk time-varying relations which are always in the set comfort interval range and the total number of the second jerk time-varying relations obtained in the step S40, and if the proportion is not less than the preset proportion, enabling the preset transmission gear time-varying relation to meet the comfort requirement.
In the calibrated model of the vehicle drive train, T e (t), i (t), V (t) and
Figure BDA0003536994810000161
is unknown, B, C, D, E, C d 、x、g(i(t))、τ(i(t))、g f 、η f 、r w A and g are all fixed; m, rho, beta, V w And V 0 The simulation device is preset manually for the actual requirements simulated by an operator according to needs.
A step may be added between step S10 and step S20:
s11, inputting m, rho, beta and V into the automobile transmission system model after benchmarking correction w And V 0 The specific numerical value of (1).
In addition, as V 0 Is defaulted to 0, so that the vehicle transmission system model can only simulate the time-varying relation of the simulated vehicle speed after the vehicle is stopped, the input of V is not needed in the step S11 0 The specific numerical value of (1).
Namely:
s11, inputting m, rho, beta and V into the automobile transmission system model after calibration correction w Specific numerical values.
Thus, after step S11, only T is included in the corrected model of the vehicle driveline e (t), i (t), V (t) and
Figure BDA0003536994810000171
is in an unknown state, so that a plurality of second engine torques to be simulated can be input into the automobile transmission system model after calibration correction according to the driving state of the automobile to be simulatedAnd the time-varying relation and the preset speed-varying relation of the speed changer are changed along with the time, each second engine torque time-varying relation and the preset speed-varying relation form an input group along with the time, so that a plurality of input groups are formed in total, and the plurality of input groups are respectively input into the automobile transmission system model after the calibration correction, so that a plurality of second vehicle speed time-varying relations can be finally obtained. The time-varying relation of the second engine torques and the preset time-varying relation of the transmission gears are artificially preset according to the vehicle running state which is simulated as required.
The number of the second engine torque variation with time may be 10-100, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100, etc., and the plurality of second engine torque variation with time may be different from each other.
In addition, the predetermined transmission gear shift relationship over time is a function of engine torque and vehicle speed, i.e., shift logic; that is, the time-varying relationship of the second engine torque and the preset gear shifting logic are input into the vehicle transmission system model after the calibration correction, so that the time-varying relationship of the second vehicle speed can be output. Therefore, when the automobile transmission system model after the benchmarking correction is actually applied to judge whether the shifting logic meets the comfort, the automobile transmission system model can be transformed, and specifically, the shifting logic is expressed as:
i(t)＝i(T e (t),V(t))…………………(16)
therefore, the vehicle transmission system model after calibration can be converted into:
Figure BDA0003536994810000172
referring to equation (17), the vehicle driveline model is composed of three interrelated equations together, where T is present e (t), i (t), V (t) and
Figure BDA0003536994810000181
four unknown variables, causeAfter confirming any one variable, the other three variables can be obtained.
That is, in step S30, the second engine torque T at the time point corresponding to the time variation of the second engine torque is input into the automobile transmission system model e (t), a second vehicle speed V (t) at time t, a second gear i (t) of the transmission at time t, and a second acceleration at time t are obtained
Figure BDA0003536994810000182
The set of V (t) at all times constitutes a second vehicle speed time-varying relation, all times
Figure BDA0003536994810000183
Constitutes the second acceleration over time.
Thus, a plurality of second vehicle speed time-varying relationships and a plurality of second acceleration time-varying relationships can be obtained through the plurality of input sets described above.
In step S40, the second jerk is obtained by deriving the time-varying relation of the second vehicle speed twice, or the time-varying relation of the second acceleration is obtained by deriving the time-varying relation of the second jerk once. In the second jerk time-varying relationship, the jerk at time t is represented by j (t), and the set of j (t) at all times constitutes the second jerk time-varying relationship.
And correspondingly obtaining a second jerk time-varying relation for each input group. A plurality of second jerks may thus be obtained as a function of time.
In step S50, it is determined whether the jerk in each second jerk time-varying relationship falls within a set comfort zone range, and if the jerks in the single second jerk time-varying relationship fall within the comfort zone range (since the jerk of the vehicle in the starting stage may be outside the comfort zone range, the jerk in the starting stage may not be determined, and the starting stage means that the second jerk time-varying relationship meets the comfort requirement in a set time period after the vehicle speed starts from 0km/h, and the set time period may be 0.7S to 1.2S.); if the comfort level exists in the single second jerk change-over-time relation and is located outside the range of the comfort interval, the second jerk change-over-time relation is not in accordance with the comfort requirement, the judgment is carried out on each second jerk change-over-time relation, therefore, the number N1 of the second jerk change-over-time relation in accordance with the comfort requirement can be obtained, further, the proportion of the N1 to the total number N2 of the second jerk change-over-time relation is obtained, and if the proportion is not smaller than the preset proportion, the preset gear shifting logic is in accordance with the comfort requirement.
Wherein the expression formula of the proportion can be expressed as:
Figure BDA0003536994810000184
the predetermined ratio is 80% to 100%, for example 80%,85%,90%,95% or 100%.
The step S50 further includes:
if the ratio is smaller than the preset ratio, the preset time-varying relation of the transmission gear (the aforementioned shift logic, equation (16)) does not meet the comfort requirement, the preset time-varying relation of the transmission gear is adjusted, and then the process goes to step S20.
The "adjustment of the predetermined transmission gear position over time" is an adjustment of a predetermined shift logic. And then verifying again until comfortable gear shifting logic is obtained.
The method provided by the invention can be used for verifying whether the preset gear shifting logic meets the comfortableness under the input conditions of the time-varying relation of the second engine torques, and provides data support for obtaining the gear shifting logic meeting the comfortableness.
It will be understood that the embodiments described above are illustrative only and not restrictive, and that various obvious or equivalent modifications and substitutions may be made in the details herein before described by those skilled in the art without departing from the basic principles of the present application and are intended to be included within the scope of the appended claims.

Claims (10)

1. A benchmarking correction method of an automobile transmission system model based on a genetic algorithm is used for evaluating whether automobile gear shifting logic accords with comfort; the method is characterized by comprising the following steps:
s100, carrying out linear acceleration test on an actual vehicle, and acquiring a first vehicle speed, a first torque output by an engine and a first gear of a transmission of the actual vehicle in the process to obtain a time-varying relation of the first vehicle speed, a time-varying relation of the first engine torque and a time-varying relation of the first transmission gear;
s200, establishing an initial automobile transmission system model, wherein the initial automobile transmission system model comprises a corresponding relation between a longitudinal force of a driving wheel, a longitudinal force of a driven wheel and a speed; the longitudinal force of the driving wheel is determined according to the torque of an engine, the gear of a transmission, the transmission ratio corresponding to the gear of the transmission, the transmission efficiency corresponding to the gear of the transmission, the transmission ratio of a speed reducer and the transmission efficiency of the speed reducer; said driven wheel longitudinal force F xf Comprises the following steps:
F xf ＝Dsin(Carctan(Bx-E(Bx-arctan(Bx))))；
wherein, B is a rigidity factor coefficient, C is a curve shape factor coefficient, D is a peak factor coefficient, E is a curve curvature factor coefficient, and x represents the slip ratio of the driven wheel;
s300, determining an optimized value of each coefficient in an initial automobile transmission system model by using a genetic algorithm; the parameter population in the genetic algorithm comprises a plurality of groups of parameter groups, wherein each group of parameter comprises a coefficient B, C, D, E; the fitness function and the termination condition are determined according to the relation that the simulated vehicle speed output by the initial automobile transmission system model changes along with time and the first vehicle speed changes along with time as a target when the first engine torque changes along with time and the first transmission gear changes along with time are used as input;
and S400, substituting the optimized values of the coefficients in the parameter population obtained in the step S300 into the initial automobile transmission system model to obtain the automobile transmission system model after the benchmarking is corrected.
2. The method of claim 1,
in step S200, the initial automobile transmission system model is:
Figure FDA0003536994800000011
where n is the number of wheels on the front and rear axles, i (T) is the gear i of the transmission at time T, g (i (T)) is the gear ratio of the transmission in gear i (T), τ (i (T)) is the transmission efficiency of the transmission in gear i (T), and T (i (T)) is the transmission efficiency of the transmission in gear i (T) e (t) is the output torque of the engine at time t, g f Is the gear ratio of the speed reducer, eta f For the transmission efficiency of the speed reducer, r w Is the radius of the driving wheel, C d Is the wind resistance coefficient, rho is the air density, A is the windward area of the automobile, V (t) is the simulated speed at the moment t in the automobile transmission system model, V w Is the wind speed, m is the mass of the car,
Figure FDA0003536994800000022
the acceleration is the simulated acceleration at the moment t in the automobile transmission system model, g is the gravity acceleration, and beta is the ramp angle.
3. The method according to claim 2, wherein in step S300, each of the parameter sets further comprises a coefficient C d 。
4. The method of claim 3,
in step S300, each coefficient B, C, D, E and C in the parameter population d The value range of (A) is as follows,
5≤B≤50，1≤C≤10，1≤D≤10，0.5≤E≤5，0.2≤C d ≤0.4。
5. the method according to any one of claims 1 to 4,
in step S300, the fitness function is
Figure FDA0003536994800000021
Wherein y is the simulation run time, S y Is the total number of times of sampling in the y-th simulation, V (t) y And V (t)' is the simulated vehicle speed at the t moment output by the initial vehicle transmission system model during the y-th simulation, and is the actual vehicle speed at the t moment in the time variation relation of the first vehicle speed.
6. The method of claim 5,
the termination condition is that MSE (y) is less than a preset value, and the preset value is 0-0.25.
7. The method according to any one of claims 1 to 6,
the step S300 includes the steps of:
s310, randomly generating an initial parameter population; the initial parameter population comprises N groups of parameter groups, wherein N is greater than or equal to 20 and less than or equal to 50;
s320, respectively taking each parameter group as an individual, taking a first engine torque time-varying relation and a first transmission gear time-varying relation as input to simulate an initial automobile transmission system model, obtaining a simulated vehicle speed time-varying relation of each individual, and respectively calculating a fitness corresponding to each individual, wherein the fitness is a numerical value obtained according to a fitness function;
s330, judging whether an individual meeting a termination condition exists, if so, executing a step S350; otherwise, executing step S340;
s340, selecting a preset number of individuals with the lowest fitness as parents, performing cross and/or variation to obtain a new parameter population, and returning to the step S320;
and S350, outputting the individuals meeting the termination condition as a better parameter group, and determining the optimized value of each coefficient in the initial automobile transmission system model according to the better parameter group.
8. The method according to claim 7, wherein in step S350, when there are a plurality of individuals satisfying the termination condition, the individual with the smallest fitness is used as the optimized value of each coefficient.
9. A method for judging whether shift logic meets comfort by using an automobile transmission system model, the method is characterized by comprising the following steps:
s10, obtaining a corrected automobile transmission system model by using the correction method of any one of claims 1-8;
s20, acquiring a preset time-varying relation of the transmission gear and a plurality of corresponding second engine torques; wherein the predetermined transmission gear shift is a function of engine torque and vehicle speed over time;
s30, respectively taking the time-varying relations of the second engine torques and the time-varying relations of the preset transmission gears as the input of the calibrated automobile transmission system model to obtain the time-varying relations of the second vehicle speeds;
s40, obtaining a plurality of second jerk time-varying relations according to the plurality of second vehicle speed time-varying relations;
and S50, judging whether the jerk in the second jerk time-varying relations is in a set comfort interval range or not, obtaining the proportion of the number of the second jerk time-varying relations which are always in the set comfort interval range and the total number of the second jerk time-varying relations obtained in the step S40, and if the proportion is not less than the preset proportion, enabling the preset transmission gear time-varying relation to meet the comfort requirement.
10. The method according to claim 9, wherein the step S50 further comprises:
if the ratio is smaller than the preset ratio, the change relation of the preset transmission gear with time does not meet the comfort requirement, the change relation of the preset transmission gear with time is adjusted, and then the step S20 is carried out.
CN202210220458.2A 2022-03-08 2022-03-08 Benchmarking correction method and comfort judgment method for automobile transmission system model Pending CN115146370A (en)

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