Simulation of Vehicle Usage and Representation on Test Track

With U·Sim (Usage Simulation), customer usage simulations can be performed to extrapolate data to the entire life of the vehicle. Customers are generated according to usage profiles using Monte Carlo simulation and are represented by real measurement data. The quantile customers define a design target in combination with safety factors and special maneuvers (e.g. kerbstone crossings).

Based on a reference load, U·SimOpt (Usage Simulation-Optimization) is used to determine optimal track combinations to derive test scenarios. For this purpose, the reference load is mapped to the test track measurements by means of optimization. Restrictions due to the structure of the proving ground can be taken into account. A compressed description of the loads can be determined for simulations with MBS and FEM.

Extrapolation of Data to Distributions with U·Sim

© Fraunhofer ITWM

After planning and evaluating measurement campaigns, the data is extrapolated to load distributions. To do this, you need information on how the factors (influencing quantities) and levels affect loads or consumption. Examples are:

  • Type of road (city, country, motorway, road)
  • Mass, load and type of loading of the vehicle (e.g. static or fluid load)
  • climate
  • Driving style (moderate, aggressive) etc.

Variance and regression analyses provide information on the influence of individual factors, possible interaction effects (e.g. offensive driver meets heavily loaded vehicle) and their statistical significance. The combinations of factor levels (operating states) will therefore generally have different effects. Depending on this analysis, the appropriate factor model for the respective application will be determined.

If there are frequency distributions (usage model) for the individual operating states of the model that correspond to the expected use of the vehicle by a certain customer group, U·Sim calculates a distribution of the relevant variables for this group (operating load, consumption, etc.) from the measurement data using Monte-Carlo simulation. The usage model can, for example, be determined using VMC methods. In particular, sensitivity studies on the effects of different user behaviour can be carried out very efficiently.

Optimal Test Mixing with U·SimOpt

© Fraunhofer ITWM
Optimal Track Mixing with U·SimOpt

U·SimOpt is used to determine optimal track combinations for test scenarios. Input data for the program are measurements on different test tracks of a proving ground or in customer operation, from which a test scenario is to be compiled.

This data includes, among other things:

  • Pseudo damage for all relevant signals
  • Properties of the tracks or lanes (length, duration, ...)
  • Restrictions on the use of the lanes
  • Reference loads (determined by U-Sim, for example)

The aim is to determine a mixture of the test tracks which deviates as little as possible from the specified reference load. Since this should be fulfilled for many signals at the same time, a compromise must be found. U·SimOpt calculates the optimal number of repetitions for each track under given boundary conditions. Various target functions of the optimization problem (such as minimum running time, minimum deviation from the given loads or maximum quality of the program) can be selected. Various constraints are also taken into account.

Further functions:

  • Graphical analysis of data, tracks and test schedules
  • Modification of the constraints and iterative adaptation of the solution
  • Microsoft Excel interface for data import and export