Heavy vehicles and road machines - Tire models - Road plan - Road excitation -Maneuvers - Library of suspensions and elements of transmission
UM Automotive is the new additional module for program package Universal Mechanism, which is intended for simulation of road vehicle dynamics. UM Automotive widens the functionality of UM Base configuration and includes program tools for description of a road plan and road excitations, mathematical models of tires and drivers and a library of maneuvers, suspensions, steering systems and elements of transmission.
Heavy vehicles and road machines
To compare and determine if there is acceptable agreement between simulations from Universal Mechanism and other computer-based modeling packages special verification was done. Two test models of heavy vehicles were created in different modeling programs and results of simulation their dynamics were obtained. National road transport commission of Australia carried out numerical experiments in ADAMS/CAR, UMTRI’s constant velocity Yaw/Roll program and AUTOSIM and our laboratory did the same in Universal Mechanism.
Computer models of a truck/trailer and a B-double are considered. In total four simulations were devised that would test and compare a range of features in the models. Pulse steer and step steer inputs were used in the two simulations that employed open-loop steer control, and closed-loop control was used in path following tasks of a high-speed lane change and a low-speed 90° turn.
Detailed description of both models, all of maneuvers and comparative results of numerical simulations for ADAMS/CAR, UMTRI,s constant velocity Yaw/Roll program and AUTOSIM were published in a report of National road transport commission of Australia. This report was released into the public domain and available for downloading here.
In our laboratory identical simulations using the same test maneuvers comprising a pulse steer, step steer, standard SAE lane change and a low-speed 90° turn were performed. Results of these tests are available here.
Comparison of reports shows very good agreement between Universal Mechanism and other modeling packages.
Library of suspensions includes the following kinds of suspensions:
- double wishbone;
- trailing link;
- semi-trailing arm;
- tri-link strut;
- leaf-spring suspension.
Library of steering systems includes:
- drag link steering;
- rack and pinion steering.
- differential gear;
- Cardan shafts, etc.
Library of elements of transmission includes:
Library of suspensions and elements of transmission
UM Automotive includes the library of the most widespread kinds of suspensions, steering systems and elements of transmission. Library is the set of UM models, which can be easily built in a complete model of a vehicle using subsystem technique (see subsystem module) All models in the library have full parameterization that accelerates the description of the final model as well as analysis and optimization of its dynamical behavior. The library is completely open for any changes. The user can change any model in the library and add his/her own models in the library.
The module includes two tire models, which describe dynamical forces and torques between a wheel and a road. Implemented models are widely used for simulation of vehicle dynamics and provide accurate solution in the case of adequate setting their parameters. UM Automotive includes the following tire models:
- Magic formula;
UM Automotive contains a special tool for description of macro geometry of a road: turning, hill, hillside, etc.
UM Automotive contains a tool for description of a road profile, which supports several ways to describe the irregularities
- pointwise input (for measured data);
- analytical expressions;
- synthesis of the road profile based on its spectral power density;
- superposed pointwise/analytical/generated by spectral power density road profile.
Several files with spectral power density of typical road surfaces and corresponding road profiles are included in the module. They are: concrete, asphalt in good and satisfactory condition, and cobblestone road.
Several mathematical models of driver and a set of typical maneuvers such as straight-ahead braking, double lane-change, braking in a turn, power-off reaction of a vehicle in a turn, power-off in turn, steady-state circular driving behavior and others (including ISO standards) are available. Analysis of vehicle dynamics with the help of such wide set of typical maneuvers helps you have a clear idea of dynamical behavior of the vehicle.