Multibody Vehicle Model Research Articles

An explicit integration method for realtime simulation of multibody vehicle models

High performance computers have been used for realtime simulation of multibody vehicle dynamics models consisting of many bodies and joints, a powertrain model, antiroll bars, and tires. This research proposes an efficient implementation algorithm for explicit numerical integration methods so that relatively low cost computers can be used for the realtime simulation of the multibody vehicle dynamics models. Newton chord method is employed to solve the equations of motion and constraints. The equations of motion and constraints are formulated such that the Jacobian matrix for Newton chord method is needed to be computed only once for a dynamic analysis. Numerical experiments showed that the Jacobian matrix generated at the initial time could have been utilized for the Newton chord iterations throughout simulations under various driving conditions. Convergence analysis of Newton chord method with the proposed Jacobian updating method is carried out. The proposed algorithm yielded almost exact solutions for a prototype vehicle multibody model in realtime on a 400 MHz PC compatible.

A real-time multibody vehicle dynamic analysis method using suspension composite joints

This paper presents a real-time vehicle dynamic analysis method using suspension composite joints. Typical suspension systems of vehicles such as MacPherson strut, double wishbone, trailing arm and solid axle suspension systems are modelled by suspension composite joints. The joints are derived and utilised to reduce the computation time of simulation without any degradation of kinematical accuracy of the suspension systems. They are modelled using massless links on the suspension members that have small masses but have kinematical importance. Using the developed suspension composite joints, a multibody vehicle dynamic model is formed and simulations are performed. Accuracy of the simulation results is compared to the real vehicle field test results as well as to the simulation results with a full multibody vehicle model. It is found that the simulation results using the proposed method are very accurate and real-time simulation is achieved on a computer with single PowerPC 604 processor.

A Generic Multibody Vehicle Model for Simulating Handling and Braking

SUMMARY A vehicle system dynamics model is presented that captures the essential braking and handling behavior of an automobile with independent suspensions on a flat surface. The model, which has 18 degrees of freedom, is described in sufficient detail for an engineer to reproduce it with a multibody simulation program. Further, a stand-alone computer program based on the model has been put on the internet for interested readers to download and run. The model has a simple generic representation of suspension kinematics that can represent the behavior of most independent suspensions. The generic model is demonstrated using a previously published vehicle description (the IAVSD Iltis multibody benchmark) and compared with a detailed multibody model. Close agreement was found between the two models both for eigenvalues and for nonlinear time history responses.

MBS Modelling, Non-linear Simulation and Linear Analysis Techniques for Integrated Vehicle Control

The study described in this paper is aimed at the development of appropriate vehicle modelling techniques to support research into total motion control systems for future vehicles. The requirement for automatic generation of realistic full vehicle multibody system models capable of non-linear dynamic simulation and linear analysis is explained. The application of the modelling techniques described is then illustrated by a Jeep model. The model and its use for non-linear ride and handling predictions, modal analysis and ride quality assessment is discussed, and conclusions drawn as to the suitability of the modelling approach.

Linearized Flexible Multibody Dynamics Including Geometric Stiffening Effects∗

Abstract In multibody system simulation for vehicle dynamics applications, it is often sufficient to consider a set of system equations in which the kinematics are linearized. On the other hand, care must be taken to model the flexibility of the system bodies correctly and to be able to introduce the highly nonlinear force laws appearing in multibody vehicle models into the simulation. A formalism meeting these objectives is presented here. Special care has been taken to incorporate geometric stiffening terms that result from nominal loads on the system. This formalism is the core of the vehicle dynamic simulation code MEDYNA.

Exact Equations for Tractrix Curves Associated with Vehicle Offtracking

Abstract Vehicle offtracking behavior at low speeds is closely approximated by a geometric entity called a tractrix. This paper presents differential equations for generalized coordinates of a planar multibody vehicle model based on tractrix behavior. The equations are exact, can be used with any type of input path, are valid for forward and backward movements, and are much simpler than previously published formulations used to compute transient offtracking. The differential equations can be integrated using conventional numerical integration algorithms to obtain plots of the low-speed tracking performance of articulated vehicles. The equations were formulated symbolically by a computer program used to analyze the kinematic and dynamic behavior of multibody systems. Example numerical results are plotted.