Method for generating virtual prototype of vehicle having plurality of wheels

Abstract

The invention relates to a computer-implemented method for generating a virtual prototype with a vehicle on the basis of data from road measurements, comprising the following working steps: S1) providing a tire database comprising a plurality of tire data sets with Pacejka parameters; s2) providing a vehicle model, wherein the vehicle model is provided with a tire model which can be adjusted through the tire data set; s3) providing a tire data set for the tire model; s4) carrying out a measurement travel with a load event during which a measured value of a traction parameter of at least one of the tyres is determined; s5) simulating the load event with the vehicle model, at least one simulated value of the traction parameter of the tyre being output; s6) comparing the measured value of the traction parameter with the simulation value of the traction parameter; s7) adjusting the tire data set so as to adapt the simulation value of the traction parameter to the measured value of the traction parameter by changing the Pacejka parameter; wherein the working steps from S5 to S7 are repeated until a termination condition is reached; and then the value scale of the Pacejka parameter is output.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for generating a virtual prototype of a vehicle having a plurality of wheels based on data from road measurements, a computer program or storage medium containing instructions for carrying out such a method and a system for generating a virtual prototype of a vehicle based on data from road measurements. BACKGROUND

[0002] Wheels are used in vehicles to ensure the necessary transfer of power to the roadway. Particularly important for the transfer of power is the tire, which is often made of rubber material, which forms the contact between the vehicle and the roadway. It is known from the prior art to analyze the properties of wheels and tires based on physical data.

[0003] Tires play an important role in the vehicle-road system, as they transfer all forces and torques as a connection between the roadway and the vehicle. The force transmission and transfer properties of the tire explicitly influence the driving properties, comfort and safety of the entire vehicle. Pneumatic tires mainly rely on the gas enclosed under overpressure, only a small part of the wheel load is directly carried by the tire structure. The development of tires for passenger cars and trucks is decisively influenced by the constantly changing and increasing requirements for motor vehicles. Electric vehicles in particular have fundamentally increased tire wear due to the greater weight of the batteries and the greater torque and rotational gradient caused by the electric motor. The use properties of a tire describe the individual properties of the tire. Road measurements are carried out to determine the use properties. The theoretical description of the tire properties is generally known from the Pacejka thesis. Reference is made by way of example to the following scientific publication: Pacejka, H. B.; Besselink, I. I. M.: Magic Formula Tyre Model with Transient Properties. Lisse, the Netherlands. Swets & Zeitlinger Publishers, Lisse, the Netherlands, 1997, pp. 234-249.

[0004] In order to analyze the properties of a vehicle with real tires as far as possible under all relevant driving operations and road and environmental conditions, a large number of test kilometers need to be completed.

[0005] Furthermore, these real test drives are not carried out during the vehicle development, but only in the later stages of vehicle development. It is known from the prior art in principle to carry out virtual test drives with vehicle simulation tools. But these vehicle simulation tools in turn require a virtual prototype of the vehicle. SUMMARY

[0006] It is the task of the present invention to provide a virtual prototype of a vehicle having a plurality of wheels. It is in particular the task of the present invention to generate a virtual prototype of a vehicle having a plurality of wheels as automatically as possible.

[0007] This task is solved by the teaching of the independent claims. Advantageous design solutions are protected in the dependent claims.

[0008] A first aspect of the present invention relates to a computer-implemented method for generating a virtual prototype of a vehicle having a plurality of wheels based on data from a road measurement, in particular for indirectly measuring values of Pacejka parameters, the method having the following working steps: S1) providing a tire database comprising a plurality of tire data sets having Pacejka parameters; S2) providing a vehicle model comprising a digital twin of the vehicle and a tire model adjustable by means of the tire data; S3) providing a tire data set for the tire model from the tire database; S4) performing a measurement drive with the vehicle, wherein the measurement drive comprises a load event and during the load event a measured value of a traction parameter of at least one of the wheels is determined; S5) simulating the load event with the vehicle model, wherein at least one simulated value of the traction parameter of at least one of the wheels is output as a target variable; S6) comparing the measured value of the traction parameter in working step S4 with the simulated value of the traction parameter in working step S5; S7) adjusting the tire data set in order to adapt the simulated value of the traction parameter to the measured value of the traction parameter by changing the values of the Pacejka parameters; wherein working steps S5 to S7 are repeated until a termination condition is reached; and subsequently S8) outputting the values of the Pacejka parameters of the tire model.

[0009] A second aspect of the present invention relates to a method for analyzing a vehicle tire set, wherein a vehicle tire set is simulated by means of a virtual prototype of a vehicle, the virtual prototype being generated by means of the method according to any one of the preceding claims.

[0010] A third aspect of the present invention relates to a system for generating a virtual prototype of a vehicle based on data from a road measurement, in particular for indirectly measuring values of Pacejka parameters, the system comprising means for parameterizing a tire model of the virtual prototype, the tire model having Pacejka parameters, wherein the means for parameterizing are configured to iteratively successively determine values of the Pacejka parameters in a simulation loop in which parameters of the tire model are optimized by means of a software-in-the-loop simulation based on measured values of the road measurement, in particular a cascade, by comparing simulated values of the one or the plurality of traction parameters with measured values of the one or the plurality of traction parameters determined by the road measurement.

[0011] A fourth aspect of the application relates to a system for generating a virtual prototype of a vehicle based on data from a road measurement, in particular according to claim 19, having means for parameterizing a tire model, wherein the means for parameterizing comprise means for calculating at least one measured value of a traction parameter of the tire based on values of measurement variables acquired during the measurement drive, means for calculating at least one value of a slip ratio of the tire based on values of measurement variables acquired during the measurement drive, means for simulating the vehicle by means of the tire model, wherein at least the following physical properties of the vehicle are introduced as parameters into the tire model: weight, wheel base, track width, center of gravity and steering ratio, wherein at least the value of the traction parameter is output as a target variable, means for comparing the at least one measured value of the traction parameter with the at least one value of the simulated traction parameter, means for adjusting the vehicle model in order to match the simulated traction parameter to the measured traction parameter determined based on the road measurement by changing the Pacejka parameters, and an interface for outputting the values of the Pacejka parameters of the tire model, and wherein the means for parameterizing are configured to adjust the tire model for as long as it takes until a termination condition is reached.

[0012] A further aspect of the application relates to a computer program and a storage medium having instructions which, when implemented by a computer, cause this computer to implement a method according to the application.

[0013] The road measurement according to the application is preferably a field measurement, that is to say a measurement which takes place in a real driving operation of the vehicle. The tire refers to a component on which the wheel rolls. The wheel refers to the complete unit consisting of the rim and the tire.

[0014] The software-in-the-loop simulation according to the application is preferably a simulation in which components described by software are tested in a virtual model world.

[0015] The traction parameter according to the application preferably represents a property of the tire. The traction parameter in the tire is in particular a property which serves to describe the behavior of the tire when power is transmitted. The traction parameter is in particular the grip, that is to say the friction coefficient, the slip ratio or the slip angle or a variable derived therefrom. The ratio of the force F p parallel to the lane plane to the force F z normal to the lane plane is explained as the grip G or the friction coefficient: G = F p / F z . The ratio of the rolling direction of the tire to the movement direction of the tire is referred to as the slip angle. The ratio of the grip to the slip angle or the ratio of the force in the x direction to the slip angle or the ratio of the force in the y direction to the slip angle is also an example of a traction parameter.

[0016] Pacejka parameters are a set of tire model parameters used in vehicle dynamics to describe the forces and moments occurring between a tire and a road surface. Pacejka parameters are used to predict the behavior of a vehicle under different speeds, load states and road surfaces. Pacejka parameters are based on measurements derived from practice and are suitable for modeling the behavior of a vehicle. The mathematical equation used to describe the forces and moments occurring between a tire and a road surface is called the magic formula or Pacejka formula and was proposed by the Dutch engineer Hans B. Pacejka. Pacejka parameters describe characteristics such as tire stiffness, friction coefficient and tire shape, for example, in order to model the behavior of a tire.

[0017] Pacejka parameters differ from tire to tire. A tire dataset contains a number of Pacejka parameters belonging to a tire or a group of tires. There are different sets of Pacejka parameters which can vary depending on the application. The number of Pacejka parameters can thus vary for different tire datasets. In the simplest case of the Pacejka formula, the Pacejka parameters comprise only six different values. The Pacejka formula, which has been further developed, has more than 100 parameters in its latest version. Tire datasets preferably also have such a large number of parameters. Early versions of the Pacejka formula essentially only map static cases, i.e. static, constant slip characteristics only in the static range, but the latest developed versions of the Pacejka formula can also map dynamic tire characteristics.

[0018] The method is not only used to generate virtual prototypes, but can equally well be described as an indirect measurement method for indirectly measuring Pacejka parameters. The physical state of a tire is defined by the measurable physical characteristics of an object at a particular point in time. According to the invention, a method is described in which a simulation is carried out using real measurement data of a vehicle, in particular the speed, acceleration, rotational rate, rotational speed and torque of the tire. These data are used as input items and the simulation calculates the Pacejka parameters of the tire model as output items.

[0019] Pacejka parameters describe physical characteristics of a tire. Pacejka parameter A, for example, describes the lateral stiffness, which indicates how the tire responds to lateral forces, Pacejka parameter B describes the lateral peak factor, which indicates the degree of non-linearity of the lateral force depending on the slip angle, or Pacejka parameter C describes the lateral shape factor, which influences how the shape of the slip curve goes. For all other Pacejka parameters, there is a corresponding physical association.

[0020] The claimed method thus uses measurements of real objects as input, provides a physical state of the real existing object and contributes to the technical implementation of the method by each of its steps.

[0021] The digital twin of a vehicle refers to a digital representation of a real-world entity vehicle in the digital world. It does not matter whether the vehicle already exists in the real world or will exist in the future. The digital twin enables a cross-domain data exchange and is composed of models of the individual elements of the vehicle and in addition contains simulations, algorithms and services which describe properties or behavior of the vehicle.

[0022] Time-bound events are described as load events in which at least the tires of the vehicle are subjected to a load which differs from the load of a stationary or unaccelerated vehicle. The load event can be, for example, or include an acceleration operation such as full-load acceleration, a braking operation such as full-load deceleration, a curve travel with constant or varying radius or other travel operations.

[0023] If the measured traction parameter of at least one of the wheels is determined in step S4, this can mean that the traction parameter of one wheel is determined or that the traction parameter of a plurality of wheels is determined or that the individual traction parameters of a combination of wheels, for example two wheels arranged on the same axle, are determined. It is provided in particular that the measured traction parameter of at least one of the tires is determined in step S4. The tires are the relevant part of the wheels for this step. The corresponding explanations apply to the output of the simulated traction parameter in step S5. The measured traction parameter and the simulated traction parameter use the same parameter, namely the proportion of the grip to the slip ratio, but differ in their specific measured or simulated values.

[0024] In order to determine the measured values of the traction parameter during the measurement travel, in particular an IMU (Inertial Measurement Unit) is used, which has a gyroscope with which the rotational rate of the vehicle in three axles can be determined, an acceleration measuring instrument with which the acceleration of the vehicle in three directions can be determined and a GPS system with which the position of the vehicle in three dimensions can be determined. The measurement of the speed in the z direction, i.e. perpendicular to the lane, the measurement of the acceleration in the z direction and the measurement of the rotational rate of the vehicle in the z direction are optional here. Further measured variables of the measurement travel are the wheel rotational speed and the torque of the wheels.

[0025] Further advantages are achieved when in step S4) the measured values of the traction parameters of at least one of the wheels are determined by measuring the speed, acceleration and rotational rate of the vehicle parallel to the lane and the rotational speed and torque of the tires. In a particular embodiment of the application, all steps of the method which are carried out in connection with the wheels are carried out in connection with the tires.

[0026] Instead of determining the individual values of the measured or simulated traction parameters, respectively, it is preferred to determine a plurality of values of the measured traction parameters or to output a plurality of values of the simulated traction parameters, respectively. This means for the values of the measured traction parameters that some traction parameters which are measured during the load event are determined. This means for the values of the simulated traction parameters that some values of the traction parameters which are simulated by the load event are output as target variables.

[0027] The adjustment accuracy of the Pacejka parameters which are modeled can thereby be improved.

[0028] The adjustment of the tire data set in step S7 can be carried out by completely replacing the tire data set and / or by adjusting the individual Pacejka parameters in the tire data set. The purpose of this step of matching the simulated traction parameters to the calculated traction parameters can be achieved purposefully or non-purposefully. In particular, the adjustment in step S7 of the loop is set up such that the load event is simulated with the vehicle model using any tire data of the tire data sets of the tire database.

[0029] In particular, the repetition of steps S5 to S7 a certain number of times or the last simulation is reached can be used as a termination condition for the simulation of all tire data sets which are available in the tire database.

[0030] In step S8, in particular, the Pacejka parameters which result from the optimum of the comparison in step S6 and / or when the termination condition is reached are output. The output of the values of the Pacejka parameters of the tire model is equivalent to the selection of the parameters for the tire model. Because the values of the Pacejka parameters are selected for the tire model. A virtual prototype of the vehicle with a plurality of wheels is thus generated with the output.

[0031] The approach on which the application is based is that the Pacejka parameters of the tires of a vehicle can be determined by an iterative simulation method for a virtual prototype. In this way, the driving behavior of the tires of a vehicle is simulated without further test drives with a test vehicle for this purpose. The vehicle model creation can be carried out in this way in a low-cost, short time and with a provable high quality in connection with the tires. Here, the properties of the traction, i.e. the grip of the tires, can be simulated particularly accurately depending on the tire type. By means of the method according to the application, a vehicle model can be created automatically on the basis of measurement data from road measurements.

[0032] It is preferably provided in the method according to the first aspect that the traction parameter comprises a grip and / or a slip ratio and / or a slip angle.

[0033] Grip refers to the ratio of the force acting on the tire parallel to the lane to the force perpendicular to the lane. Slip ratio is the ratio of the speed with which the tire moves on the road to the speed with which the vehicle as a whole moves forward and backward. When the slip ratio is high, the tire turns faster than the vehicle. Slip angle refers to the angle between the direction of the wheel turning and the direction of movement of the wheel. It is also possible to provide traction parameters derived from these quantities.

[0034] Further advantages are achieved when steps S4 to S8 are carried out for each of the wheels, in particular for each of the driven wheels.

[0035] This explicitly means that in step S4 the measured traction parameter of each of the wheels, in particular of each of the driven wheels, is determined. This means for step S5 that at least one simulated traction parameter of each of the wheels, in particular of each of the driven wheels, is output as a target variable. This means for step S6 that the value of the measured traction parameter of each of the wheels in working step S4 is compared to the value of the simulated traction parameter in working step S5 individually with one another.

[0036] For some target specifications a good compromise between accuracy and expenditure is to determine the measured traction parameter of only each of the driven wheels and to output the simulated traction parameter of only each of the driven wheels as a target variable in the case of the load event being an acceleration, in particular a full load acceleration.

[0037] It is preferably possible to provide in the last-mentioned particular embodiment of the application that the fitting accuracy is calculated with a least squares method.

[0038] In the least squares method the quantity of data points of the simulated traction parameter is adjusted to be as close as possible to the quantity of data points of the measured traction parameter. In this particular embodiment of the application, therefore, a plurality of values of the measured traction parameter of one of the wheels is determined in step S4 and a plurality of values of the simulated traction parameter of at least one of the tires is output as a target variable in step S5.

[0039] In another advantageous embodiment the method further comprises the step of adjusting the vehicle control on the basis of the values output in step S8.

[0040] In another advantageous design the method further comprises the step of controlling and / or adjusting the vehicle on the basis of the values output in step S8.

[0041] The output values of the Pacejka parameters can be used in the vehicle as control parameters or influence control parameters in the vehicle. Thereby vehicle functions can be created which enable the vehicle to be operated particularly efficiently.

[0042] A wheel suspension is a component in a vehicle which connects the wheel to the chassis or body and has the task of controlling the vertical, lateral and horizontal movements of the wheel. The wheel suspension is composed of different parts, such as suspension elements, shock absorbers, transverse links and axles, and serves to achieve a stable and controlled ride in such a way that the wheel suspension compensates for the unevenness of the roadway and keeps the wheel in contact with the road. A correctly tuned wheel suspension maximizes the contact between the tire and the road and improves the grip in such a way that the wheel suspension keeps the tire in an optimum position in order to transmit longitudinal and lateral forces to the road.

[0043] The consideration of the wheel suspension in the vehicle model makes it possible to further optimize the generation of the virtual prototype of the vehicle.

[0044] It is preferably provided that the road covering is also taken into account in step S5.

[0045] Further advantages are achieved when the load event has an acceleration. The acceleration can in particular be a full-load acceleration.

[0046] It is provided in a further particular embodiment of the application that the load event has a deceleration. The deceleration can in particular be a full-load deceleration.

[0047] It is particularly preferred that the load event has a curve run with a constant radius and a rising speed.

[0048] Further advantages are achieved when the termination condition is the achievement of a minimum value, in particular a local or absolute minimum, of the deviation between the measured value of the traction parameter and the simulated value of the traction parameter.

[0049] It is further preferred that, in order to determine the measured value of the traction parameter in step S4, the following measured variables are detected: vehicle speed, vehicle acceleration, vehicle rotation rate, wheel rotation speed and wheel torque.

[0050] It is provided in a further preferred embodiment of the application that the adjustment of the tire data set in step S7 comprises the selection of the tire data set for the tire model from a tire database.

[0051] It is thereby possible, in particular, to change all the Pacejka parameters simultaneously. This change achieves a coarse optimization of the simulation quality in line with the development trend.

[0052] In another advantageous embodiment of the application it is provided that the adjusting of the tire data set in step S7 comprises adjusting the individual Pacejka parameters of the selected tire data set.

[0053] Thereby a particularly accurate optimization of the simulation quality can be achieved. In particular, it is also possible to adjust the individual values of the selected tire data set in close proximity to the optimization by selecting the tire data set.

[0054] Further advantages are achieved when the weight, the wheel base, the track, the center of gravity of the vehicle and the steering ratio are taken into account in the vehicle model.

[0055] In the system according to the fourth aspect of the application it can be preferred that the means further comprise means for calculating at least one value of the lateral force of the tire on the basis of the values of the measured variables acquired during the measurement drive.

[0056] Furthermore, the term "comprising" in a particular embodiment of the application also means "is". BRIEF DESCRIPTION OF DRAWINGS

[0057] Further features and advantages are derived from the description with reference to the drawings. In the drawings:

[0058] Figure 1 at least one embodiment of a method for generating a virtual prototype of a vehicle is shown at least partially schematically;

[0059] Figure 2 a plot of measured values and simulation values of the traction parameter of an unadjusted tire data set is shown at least partially schematically;

[0060] Figure 3 a plot of the measured values and simulation values of the traction parameter of a tire data set adjusted with respect to each other is shown at least partially schematically; and Figure 2

[0061] Figure 4 at least one embodiment of a system for generating a virtual prototype of a vehicle is shown at least partially schematically. DETAILED DESCRIPTION

[0062] Figure 1 One embodiment of a method S0 for generating a virtual prototype of a vehicle 10 on the basis of data from a road measurement is shown.

[0063] In step S1 a tire database 12 is provided, which comprises a plurality of tire data sets 14 with Pacejka parameters.

[0064] ​In step S2 a vehicle model 15 is provided, which comprises a digital twin 16 of the vehicle and a tire model 18 which can be adjusted by the tire dataset 14.

[0065] In step S4 a measurement drive is performed with the vehicle 10, wherein the measurement drive comprises a load event and values of the traction parameter of a plurality of tires during the load event are determined. The values are determined by a measurement and calculation step. The values are referred to as "measured values" of the traction parameter. The load event is an acceleration. The traction parameter is the ratio of the force acting on the two tires of a driven axle to the slip acting on the two tires of a driven axle. For this purpose, the two tires of a driven axle are combined. The detection of the measurement values can be done on the one hand by a data interface, but also directly by its sensors during the measurement drive.

[0066] Steps S1, S2 and S4 are independent of each other in their sequence. Step S3 necessarily requires the tire database 12 and the tire model 18. Step S3 is therefore performed directly after steps S1 and S2.

[0067] For the road measurement, a measurement drive is performed with the vehicle 10 on a lane, in particular on a road. The vehicle 10 is equipped for this purpose with measuring instruments and sensors. The vehicle 10 has in particular an inertial measurement unit IMU for measuring the rotation rates in three axles, measuring the accelerations in three directions and measuring the position of the vehicle in three dimensions. Furthermore, during the measurement drive, the wheel rotation speeds, the speed of the vehicle in the longitudinal and lateral direction, the rotation rates of the vehicle in the longitudinal and lateral direction and the torques acting on each tire in the wheels are determined. Furthermore, the following vehicle parameters are set as a prerequisite for the road measurement: the static weight of the vehicle, the wheelbase, the track, the center of gravity in three dimensions and the steering transmission ratio, i.e. the ratio of the steering wheel rotation to the rotation of the wheels on the ground. Further optional measurement variables are the speed, the acceleration and the rotation rate of the vehicle perpendicular to the lane direction.

[0068] After steps S1 to S4, in step S5 the load event performed with the vehicle 10 in the measurement drive is simulated with the vehicle model. The simulated value 24 of the traction parameter of at least one of the tires is output as a target variable here.

[0069] The weight of the vehicle, the wheelbase of the vehicle, the track of the vehicle, the center of gravity of the vehicle and the steering transmission ratio are taken into account in the vehicle model. Furthermore, the vehicle model also takes into account the wheel suspension. All the mentioned parameters influence the slip and the forces acting on the wheels in different directions and are mapped in the vehicle model.

[0070] The same parameter is therefore determined in steps S4 and S5 as the measured value of the measurement drive and as the simulated value of the simulation, respectively. The simulated value 24 of the traction parameter can therefore be directly compared with the measured value 22 of the traction parameter.

[0071] After working step S5, the value 22 of the traction parameter measured in working step S4 is compared with the value 24 of the traction parameter simulated in working step S5 in working step S6.

[0072] The fit accuracy is calculated for the comparison. The calculation is done by means of least squares.

[0073] In combination Figure 2 Further details on the comparison are explained.

[0074] In step S7 the tire data set is adjusted in order to match the simulated value 24 of the traction parameter with the measured value 22 of the traction parameter by changing the values of the Pacejka parameters of the tire model. For this purpose, another tire data set is first selected from the tire database for the tire model. Steps S5 and S6 are repeated with this new tire data set, i.e. the load event is simulated with the vehicle model and the simulated value 24 of the traction parameter thus obtained is compared with the measured value 22 of the traction parameter as determined in working step S4. For this purpose, working step S4 is not repeated, i.e. the measurement drive with the vehicle 10 is not performed. The measured values obtained when performing the measurement drive once are called.

[0075] Working steps S5 to S7 are repeated until a termination condition is reached. In the first selected example, the termination condition is reached as soon as all tire data sets 14 present in the tire database 12 have been used to simulate the load event with the vehicle model and to compare the simulated value 24 of the traction parameter as determined by this simulation with the measured value 22 of the traction parameter.

[0076] In each comparison, the fit accuracy is determined. The determination is done by means of least squares. The tire data set for which the fit accuracy is highest at this point in time is then selected.

[0077] The method can be ended here by outputting the tire data set of the tire model 18 of the vehicle model formed with the Pacejka parameters in step S8. In this way, the generation of the virtual prototype of the vehicle 10 is ended.

[0078] But it can also be provided alternatively or additionally that, before the values of the Pacejka parameters are output, working steps S5 to S7 are repeated once more by further adjusting one or more individual values of the Pacejka parameters in the tire data set 14 for which the fit accuracy is highest. Steps S5 and S6 are performed again with the adjusted Pacejka parameters in order to further optimize the matching of the simulated traction parameter with the measured traction parameter. This adjustment is also repeated frequently in working steps S5 to S7 until a termination condition is reached.

[0079] This termination condition is in particular predetermined by the optimization problem. This termination condition can preferably be that a deviation between the measured value 22 of the traction parameter and the simulated value 24 of the traction parameter reaches a particular local or absolute minimum.

[0080] Furthermore, the termination condition can be that a limit value of the simulated value 24 of the traction parameter is reached, in particular when the simulated value 24 of the traction parameter only still changes infinitesimally.

[0081] During the measurement drive, it is possible here, alternatively, to perform, for example, the following driving operations also in accordance with the traction parameter to be determined: TipIn, TipOut, full-load acceleration, partial-load acceleration, uphill, downhill.

[0082] Figure 2 A diagram of the measured value and the simulated value of the traction parameter without a tire dataset 14 matching the measured value is shown. The measured value 22 of the traction parameter is shown with dots. The simulated value 24 of the traction parameter is shown with cross marks. In Figure 2 In a, the force of the traction parameter in the x direction, i.e. in the driving direction, is plotted for the traction parameter slip ratio. The measured values are taken from the vehicle during the load events of the measurement drive. The measured traction parameters are the force in the x direction, the force in the z direction and the grip force. The force in the x direction and the force in the z direction are the forces acting onto the two wheels of the driven front axle, respectively. The measured values are determined by measuring the position, the speed and the rotation of the vehicle in several directions, wherein the value of the weight of the vehicle 10, the wheel base, the track width, the center of gravity and the steering ratio of the vehicle are introduced as input variables into the calculation.

[0083] In Figure 2 The force acting onto the tire pair in the longitudinal direction is plotted in a with respect to the slip ratio.

[0084] The slip ratio S is determined here by wherein Ω denotes the angular speed of the wheel, R C is the effective radius of the freely rolling tire, which is calculated from the total number of wheel revolutions per kilometer. The parameter v denotes the forward speed of the vehicle.

[0085] The slip ratio indicates how much the wheel slips relative to the speed of the vehicle 10 or rotates more slowly. A slip ratio of 0 means that the wheel does not slip and rotates at the same speed as the vehicle 10, and a slip ratio of 1 means that the wheel rotates twice as fast as the ground forward speed.

[0086] For the measured values, it can be seen in Figure 2 a that the force in the longitudinal direction Fx rises with the rising slip ratio. The force in the z direction, however, falls with the rising slip ratio. The ratio of these two parameters corresponds in Figure 2The grip force plotted in c also increases with the slip ratio. In addition to the measured forces, for the first tire dataset... Figure 2 Simulated values ​​of forces and gripping forces along the x and z directions are also plotted in a, 2b, and 2c.

[0087] As can be seen in the selected examples, the measured force and grip along the x-direction are, in principle, higher than the simulated force or simulated grip along the x-direction. The force along the z-direction behaves in the opposite way.

[0088] exist Figure 3 The relative slip ratio in ac plots consistent measured values ​​of the traction parameters FxFz 22. Simulated values ​​of the traction parameters were created using another adjusted tire dataset. The simulated values ​​of the traction parameters 24 are shown in conjunction with... Figure 2 The same method is used to simulate load events using a vehicle model. It can be seen that the deviation between the measured value 22 of the traction parameter and the simulated value 24 of the traction parameter is... Figure 2 The example shown is significantly smaller. The simulated values ​​of all three traction parameters lie centrally within the discrete distribution range of the measured values ​​22 of the traction parameters across the entire range of the measured slip ratio. A threshold for fitting accuracy can be reached when this consistency is achieved between the measured traction parameter values ​​and the simulated traction parameter values. This corresponds to reaching the termination condition. After reaching the termination condition, the optimally adjusted values ​​of the Pacejka parameters of the output tire model are given, i.e., for the tire dataset used in this simulation. The output is used to create a virtual prototype of vehicle 10. The preceding steps of the method ensure that the tire model of the virtual prototype corresponds to the real vehicle 10.

[0089] Figure 4 An embodiment of a system 40 for generating a virtual prototype of vehicle 10 based on data from road measurements is shown. The system has devices 41, 42, 43, 44, and 45 for parameterizing a tire model 18 of the virtual prototype. The devices 41, 42, 43, 44, and 45 are configured to determine the values ​​of the Pacejka parameters of the tire model 18 in a simulation loop based on measurements from road measurements, through cascaded software-in-the-loop simulation. In the simulation loop, the parameters of the tire model 18 are optimized such that the iteratively simulated values ​​24 of the traction parameters are compared with the measured values ​​22 of the traction parameters obtained from road measurements.

[0090] The system 40 is specifically configured to implement pressing Figure 1 The method. Preferably, but not ultimately, the system 40 has a device 41 for calculating at least one value of the longitudinal force of the tire based on the values ​​of measurement parameters acquired during the measurement driving.

[0091] Furthermore, the system 40 preferably has a device 42 for calculating at least one value of the lateral force of the tire on the basis of the values of the measured variables acquired during the measuring drive.

[0092] The system 40 further preferably has a device 43 for calculating at least one value of the slip ratio of the tire on the basis of the values of the measured variables acquired during the measuring drive.

[0093] The system 40 further preferably has a device 44 for simulating the vehicle by means of the tire model 18, wherein at least the following physical properties of the vehicle are introduced as parameters into the tire model 18: the weight of the vehicle, the wheelbase, the track, the center of gravity and the steering ratio; wherein at least the value of the traction parameter is output as a target variable.

[0094] The system 40 further preferably has a device 45 for comparing at least one measured value of the traction parameter based on the road measurement with the simulated value 24 of the traction parameter.

[0095] The system 40 further preferably has a device 46 for adjusting the vehicle model 18 in order to match the simulated value 24 of the traction parameter to the measured value 22 of the traction parameter by changing the Pacejka parameters.

[0096] Furthermore, the system 40 preferably also has an interface 47 for outputting the values of the Pacejka parameters of the tire model. The device for parameterization is preferably set up in such a way that the tire model is adjusted for a long time until a termination condition is reached.

[0097] The devices 41, 42, 43, 44, 45 and 46 of the system 40 and the interface 47 are preferably part of a data processing device. The method S0 is preferably carried out automatically and / or computer-implemented by such a data processing device.

[0098] The devices 41, 42, 43, 44, 45, 46 and the interface 47 described are in particular also set up to carry out a plurality of simulation cycles of the method S0.

[0099] It is noted that the embodiments relate only to examples which should not limit the scope of protection, the application and the configuration in any way. Rather, a person skilled in the art derives from the foregoing description guidance to implement at least one embodiment, in particular with regard to the function and arrangement of the components, without departing from the scope of protection which results from the claims and these equivalent feature combinations.

[0100] List of reference signs 10 vehicle 12 tire database 14 tire data set 16 digital twin 18 tire model 22 measured value of a traction parameter 24 simulated value of a traction parameter 40 system 41 means for calculating at least one value of a longitudinal force of a tire 42 means for calculating at least one value of a lateral force of a tire 43 means for calculating at least one value of a slip ratio of a tire 44 means for simulating a vehicle by means of a tire model 45 means for comparing at least one road-measurement-based calculated value of a traction parameter with a simulated value of a traction parameter 46 means for adjusting a vehicle model 47 interface S0 method

Claims

1. A computer-implemented method (S0) for generating a virtual prototype of a vehicle (10) with multiple wheels based on data from road measurements, particularly for indirectly measuring Pacejka parameters, the method comprising the following steps: S1) providing a tire database (12) comprising multiple tire datasets (14) having Pacejka parameters; S2) providing a vehicle model comprising a digital twin (16) of the vehicle (10) and tire models (18) adjustable from the tire datasets (14); S3) providing tire datasets (14) from the tire database (12) for the tire models (18); S4) performing a measurement drive with the vehicle (10), wherein, The measured driving includes a load event and during the load event, the measured value (22) of the traction parameter of at least one tire is obtained; S5) The load event is simulated using a vehicle model, wherein at least one simulated value (24) of the traction parameter of at least one tire is output as a target parameter; S6) The value (22) of the traction parameter measured in step S4 is compared with the value (24) of the traction parameter simulated in step S5; S7) The tire dataset (14) is adjusted so that the simulated value (24) of the traction parameter matches the measured value (22) of the traction parameter by changing the value of the Pacejka parameter; wherein steps S5 to S7 are repeated until the termination condition is met; and then S8) The value of the Pacejka parameter of the tire model (18) is output.

2. The method according to claim 1, wherein, In step S4), the measured values ​​of the traction parameters of at least one wheel are determined by measuring the vehicle's speed, acceleration, and rotational rate parallel to the lane, as well as the wheel's rotational speed and torque (22).

3. The method (S0) according to claim 1 or 2, wherein, The traction parameters include grip force and / or slip ratio and / or slip angle.

4. The method (S0) according to any one of the preceding claims, wherein, Steps S4 to S8 are performed for each of the driven wheels.

5. The method (S0) according to any one of the preceding claims, wherein, The termination condition includes a threshold for achieving the required fitting accuracy.

6. The method according to claim 5 (S0), wherein, The fitting accuracy was calculated using the least squares method.

7. The method (S0) according to any one of the preceding claims further includes the following step: controlling and / or adjusting the vehicle (10) based on the value output in step S8.

8. The method (S0) according to any one of the preceding claims, wherein, The wheel suspension of the vehicle (10) is taken into account in the vehicle model.

9. The method (S0) according to any one of the preceding claims, wherein, Road cover was also taken into account in step S5.

10. The method (S0) according to any one of the preceding claims, wherein, The load event has acceleration.

11. The method (S0) according to any one of the preceding claims, wherein, The load event has a deceleration rate.

12. The method (S0) according to any one of the preceding claims, wherein, The load event is a curve with a constant radius and an increased speed.

13. The method (S0) according to any one of the preceding claims, wherein, The termination condition is that the deviation between the measured value (22) of the traction parameter and the simulated value (24) of the traction parameter reaches a minimum, particularly a local or absolute minimum.

14. The method (S0) according to any one of the preceding claims, wherein, In order to determine the measured values ​​(22) of the traction parameters, the measured parameters, namely vehicle speed, vehicle acceleration, vehicle rotation rate, wheel speed and wheel torque, are detected in step S4.

15. The method (S0) according to any one of the preceding claims, wherein, Adjusting the tire dataset (14) in step S7 includes selecting the tire dataset (14) for the tire model (18) from the tire database (12).

16. The method (S0) according to any one of the preceding claims, wherein, Adjusting the tire dataset (14) in step S7 includes adjusting the individual Pacejka parameters of the selected tire dataset (14).

17. The method (S0) according to any one of the preceding claims, wherein, The vehicle model takes into account the weight, wheelbase, track width, center of gravity and steering ratio of the vehicle (10).

18. A method (S0) for analyzing vehicle tire packs, wherein, The tire assembly of the vehicle (10) is simulated using a virtual prototype of the vehicle, which is generated by means of the method according to any one of the preceding claims.

19. A computer program or storage medium having instructions that, when executed by a computer, cause the computer to perform the method (S0) according to any one of the preceding claims.

20. A system for generating a virtual prototype of a vehicle (10) based on data from road measurements, particularly for indirectly measuring Pacejka parameters, the system comprising devices for parameterizing a tire model (18) of the virtual prototype, the tire model having Pacejka parameters, wherein, The device for parameterization is configured to iteratively determine the value of the Pacejka parameter by comparing the simulated value (24) of at least one traction parameter with the measured value (22) of at least one traction parameter obtained by road measurement in a simulation loop that optimizes the parameters of the tire model (18) through a particularly cascaded software-in-the-loop simulation based on road measurement values.

21. In particular, the system (40) for generating a virtual prototype of a vehicle (10) based on data from road measurements according to claim 19, the system having devices for parameterizing the tire model (18), wherein, The devices for parameterization include: a device (41) for calculating at least one value of the longitudinal force of the tire based on the values ​​of the measured parameters acquired during the measured driving; a device (43) for calculating at least one value of the slip ratio of the tire based on the values ​​of the measured parameters acquired during the measured driving; and a device (44) for simulating the vehicle (10) using a tire model (M), wherein at least the following physical characteristics of the vehicle (10) are introduced as parameters into the tire model (18): the weight, wheelbase, track width, center of gravity, and steering ratio of the vehicle (10); wherein at least one simulated value (24) of the traction parameter is input as a target parameter. The device (45) is used to compare at least one measured value of at least one traction parameter with at least one simulated value (24) of at least one traction parameter; the device (46) is used to adjust the vehicle model so that the simulated value (24) of at least one traction parameter is matched with the measured value (22) of at least one traction parameter obtained based on road measurements by changing the Pacejka parameter; and the interface (47) is used to output the value of the Pacejka parameter of the tire model (18); and wherein the device for parameterization is configured to adjust the tire model (18) for such a long period of time until a termination condition is met.

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