High Efficiency Semi-recursive Modeling And Numerical Simulation Of Vehicle Multibody System Dynamics

Complex multi-DOF nonlinear systems are research objects of multibody system dynamics and one of the core issues of multibody system dynamics research is high efficiency simulation modeling and numerical integration methods.The application of multibody system dynamics in automotive engineering concentrates on forward and inverse kinematics and dynamics analysis for vehicles and vehicle low-frequency dynamic responses under large scale of rotations and translations.Multibody dynamics modeling methods based on generalized coordinate system selection can be simply divided into two categories,one is based on absolute nodal coordinates and another is based on relative coordinates.The multibody formulation based on the relative coordinates is so-called semi-recursive multibody formulation for closed-loop systems.This thesis constructs some high-efficiency semi-recursive vehicle multibody dynamics models based on an improved semi-recursive multibody system dynamics theory and multi-DOFs complex vehicle configures.One of the models is validated and verified through a multibody mechanical simulation software.Several high order algorithms are compared and discussed.Then the appropriate algorithms are recommended for the novel intelligent vehicle real-time simulation.A new self-adaptive variable time-step method is developed to increase computation efficiency and accuracy while the stability is guaranteed.The computer program codes are integrated to meet the needs for the current faster than real-time simulation of intelligent vehicles.It is also utilized for the real-time simulation of intelligent vehicle dynamics.Eventually the eternal forces and loads applied on the vehicle when it moves are optimized by introducing combined application of steady wind loads and rolling friction resistance.The analysis of coupled dynamic property of semi-recursive vehicle multibody model offers theory and modeling foundation for real-time control and decision of vehicle dynamics(particularly for future intelligent vehicles).The main contents and conclusions are as follows:1.Build up the semi-recursive multibody system dynamics model and then perform the simulation and validation in MATLAB/C/C++ and ADAMSIn the double-step velocity transformation semi-recursive multibody system dynamics,a group of independent relative coordinates with minimum dimension describe the multibody system dynamic equations of motion based on velocity transformation of recursive modeling method,where subsystem synthesis,motion joints and slender-rods removal technique are involved.The final version of dynamic governing equations are ordinary differential equations(ODEs)in minimum dimension.This thesis develops a sedan vehicle and a light-truck semi-recursive multibody dynamic models within the frame of MATLAB/C/C++,respectively.Then the counterpart of sedan vehicle model is developed in ADAMS for model verification.To this end,the sedan vehicle semi-recursive model based on the MATLAB/C/C++ is validated and verified.2.Analyze and discuss the performances of different high order constant time-step numerical integration methods and develop a self-adaptive variable time-step method.The thesis develops a self-adaptive variable time step numerical method on the basis of proportional integral(PI)controller,and then analyses the performance(calculation accuracy and solution efficiency)of different high order numerical integration method on solving the semi-recursive multibody dynamic model.In the end,the thesis recommends the appropriate integration methods for faster-than-real-time simulation of complicated vehicle system.3.Analyze the coupling dynamic properties of the vehicle under the combined effects of wind load and rolling friction resistance.The thesis develops vehicle aerodynamics six force components model by numerical simulation method of wind load.Various external forces and loads imposing on the vehicle model during its movement are considered.Finally,the thesis analyzes the vehicle coupling dynamic response and system performance impact of wind loads and rolling friction resistance under different working conditions.