Detailed Vehicle Models Research Articles

Agent-Based Model Predictive Controller (AMPC) for Vehicular Stability With Experimental Results

Model predictive control (MPC) in automotive active safety applications has gained great success in recent years. Detailed vehicle models along with a receding horizon control scheme seek the optimal control distribution among actuators for enhanced performances while satisfying system constraints. To promote the re-usability and scalability of MPC-based vehicular active safety systems, an agent-based MPC (AMPC) is proposed in our previous study for a modularized control architecture. In this paper, implementation of the control scheme is demonstrated on an all-wheel-drive test platform. Both centralized and agent-based MPCs for vehicular stability are compared for their control performances as well as computational costs on embedded hardware. It is shown from experimental results that agent-based MPC is more flexible and computationally efficient in handling vehicle active safety challenges while gives no compromise to control performances compared to their holistically formulated counterparts.

Integration of geometry and small and large deformation analysis for vehicle modelling: chassis, and airless and pneumatic tyre flexibility

The goal of this study is to propose an approach for developing new and detailed vehicle models that include flexible components with complex geometries, including chassis, and airless and pneumatic tyres with distributed inertia and elasticity. The methodology used is based on integration of geometry, and small and large deformation analysis using a mechanics-based approach. The floating frame of reference (FFR) formulation is used to model the small deformations, whereas the absolute nodal coordinate formulation (ANCF) is used for the large deformation analysis. Both formulations are designed to correctly capture complex geometries including structural discontinuities. To this end, a new ANCF-preprocessing approach based on linear constraints that allows for systematically eliminating dependent variables and reducing the component model dimension is proposed. One of the main contributions of this paper is the development of the first ANCF airless tyre model which is integrated in a three-dimensional multibody system (MBS) algorithm designed for solving the differential/algebraic equations of detailed vehicle models. On the other hand, relatively stiff components with complex geometries, such as the vehicle chassis, are modelled using the finite element (FE) FFR formulation which creates a local linear problem that can be exploited to eliminate high frequency and insignificant deformation modes. Numerical examples that include a simple ANCF pendulum with structural discontinuities and a detailed off-road vehicle model consisting of flexible tyres and chassis are presented. Three different tyre types are considered in this study; a brush-type tyre, a pneumatic FE/ANCF tyre, and an airless FE/ANCF tyre. The numerical results are obtained using the general purpose MBS computer program Systematic Integration of Geometric Modelling and Analysis for the Simulation of Articulated Mechanical Systems (SIGMA/SAMS).

Integration of geometry and small and large deformation analysis for vehicle modelling: chassis, and airless and pneumatic tyre flexibility

The goal of this study is to propose an approach for developing new and detailed vehicle models that include flexible components with complex geometries, including chassis, and airless and pneumatic tyres with distributed inertia and elasticity. The methodology used is based on integration of geometry, and small and large deformation analysis using a mechanics-based approach. The floating frame of reference (FFR) formulation is used to model the small deformations, whereas the absolute nodal coordinate formulation (ANCF) is used for the large deformation analysis. Both formulations are designed to correctly capture complex geometries including structural discontinuities. To this end, a new ANCF-preprocessing approach based on linear constraints that allows for systematically eliminating dependent variables and reducing the component model dimension is proposed. One of the main contributions of this paper is the development of the first ANCF airless tyre model which is integrated in a three-dimensional multibody system (MBS) algorithm designed for solving the differential/algebraic equations of detailed vehicle models. On the other hand, relatively stiff components with complex geometries, such as the vehicle chassis, are modelled using the finite element (FE) FFR formulation which creates a local linear problem that can be exploited to eliminate high frequency and insignificant deformation modes. Numerical examples that include a simple ANCF pendulum with structural discontinuities and a detailed off-road vehicle model consisting of flexible tyres and chassis are presented. Three different tyre types are considered in this study; a brush-type tyre, a pneumatic FE/ANCF tyre, and an airless FE/ANCF tyre. The numerical results are obtained using the general purpose MBS computer program Systematic Integration of Geometric Modelling and Analysis for the Simulation of Articulated Mechanical Systems (SIGMA/SAMS).

Heavy-Duty Vehicle Platoon Formation for Fuel Efficiency

Heavy-duty vehicles driving close behind each other, also known as platooning, experience a reduced aerodynamic drag, which reduces the overall fuel consumption up to 20% for the trailing vehicle. However, due to each vehicle being assigned with different transport missions (with different origins, destinations, and delivery times), platoons should be formed, split, and merged along the highways, and vehicles have to drive solo sometimes. In this paper, we study how two or more scattered vehicles can cooperate to form platoons in a fuel-efficient manner. We show that when forming platoons on the fly on the same route and not considering rerouting, the road topography has a negligible effect on the coordination decision. With this, we then formulate an optimization problem when coordinating two vehicles to form a platoon. We propose a coordination algorithm to form platoons of several vehicles that coordinates neighboring vehicles pairwise. Through a simulation study with detailed vehicle models and real road topography, it is shown that our approach yields significant fuel savings.

A Co-Evolutionary Approach for Design Optimization via Ensembles of Surrogates With Application to Vehicle Crashworthiness

In many engineering application, where accurate models require lengthy numerical computations, it is a common design practice to perform design of experiments (DOE) and construct surrogate models that provide computationally-inexpensive approximations. Main challenges to that approach are (i) construction of high-fidelity surrogates and (ii) discovery of high performance designs despite the fidelity limitations. An ensemble of surrogates (EOS) is a collection of different surrogates approximating the same process (typically with some form of weighted averaging to get an overall approximation) and has been demonstrated in the literature to often exhibit better performance than any of the individual surrogates. This paper presents a Multi-Scenario Co-evolutionary Genetic Algorithm (MSCGA) for design optimization via EOS. MSCGA simultaneously evolves multiple populations in a multi-objective sense via the predicted performance by the different surrogates within the ensemble. The outputs of the algorithm are solution sets including several designs that are spread over Pareto-optimal space of best-predictions by the surrogates within EOS, as well as best designs as predicted by individual surrogates and the weighted average of the EOS. Studies using analytical test functions show MSCGA to be more likely to discover better performing designs than an individual surrogate or a weighted ensemble. The primary application for MSCGA presented in this paper is that of vehicle structural crashworthiness since it is a typical design application that requires massive computational resources for accurate modeling. Two studies, which include simplified and detailed vehicle models, MSCGA successfully discovers new high performance designs.

Automated Vehicle Structural Crashworthiness Design via a Crash Mode Matching Algorithm

This paper presents an automated algorithm for the design of vehicle structures for crashworthiness based on the analyses of the structural crash mode (CM). The CM is the history of the deformation of the different zones of the vehicle structure during a crash event. The algorithm emulates a manual design process called crash mode matching where crashworthiness is improved by manually modifying the design until its CM matches what the designers deem as optimal. Given an initial design and a desired crash mode, the proposed algorithm iteratively finds new designs that have better crashworthiness performance via stochastic sampling of the design space. In every iteration of the algorithm, a number of sample designs are generated through a normal distribution on neighboring regions of the search space to the current design, and the best among the samples is chosen as the new design. The mean and the standard deviation of the normal distributions are adjusted in each iteration by examining the crash mode of the current design and by applying a set of fuzzy logic rules that encapsulate elementary knowledge of the CM matching practice. Two case studies, examining a front half vehicle as well as fully detailed vehicle models, are presented to demonstrate the effectiveness of the proposed algorithm.

Cosimulation of multi-body-based vehicle dynamics and an electric power steering control system

Increasing use of electric power steering (EPS) systems, which affect vehicle dynamic behaviour, has prompted the need for a more effective method of analysing control systems coupled with detailed vehicle models. This paper develops an integrated simulation of an EPS control system with a full-vehicle dynamic model. Using a cosimulation technique, a multi-body-based full-vehicle dynamic model interacting with the EPS control algorithm is concurrently simulated on a single-bump road condition. The effects of EPS on the vehicle dynamic behaviour and handling responses resulting from steer and road input are analysed and compared with proving ground experimental data. The comparisons show reasonable agreement on tie rod load, rack displacement, steering wheel torque and tyre centre acceleration. This cosimulation capability may be useful for EPS performance evaluation and calibration, as well as for vehicle handling performance integration.

Developments in the simulation of real world car to pedestrian accidents using a pedestrian humanoid finite element model

Computer models of pedestrian humanoids and detailed vehicle models have been developed to simulate real world pedestrian accidents. The purpose of this modelling is to enable the design. development and evaluation of pedestrian safety technologies under more realistic conditions than the proposed European legislation in order to improve pedestrian safety. LS-DYNA3D has been used to provide an extensive range of modelling possibilities. This paper discusses the developments in the humanoid modelling concept, that was introduced in an earlier article. The validation of those parts of the humanoid that have been developed from original dummy parts are presented and the sensitivity of simulation results to variations in several important biological parameters are reported. Variations between adult and child simulations are presented and discussed.

Design Sensitivity Analysis of Noise, Vibration, and Harshness of Vehicle Body Structure*

ABSTRACT A continuum design sensitivity analysis (DSA) approach to noise, vibration, and harshness (NVH) of vehicle body structure is developed using Mindlin plate and Timoshenko beam theories. Linear shape functions used for numerical meth ods of DSA cause a deficiency in bending energy that is accounted for. For large scale NVH applications, linear and bilinear isoparametric elements require much less analysis time. To handle complex vehicle built-up structures, the warped plate element and general cross-sectional beam element with offset effects are included in the numerical method for DSA. A variational approach is used to obtain the continuum design sensitivity formulation. Thickness of plates and nonprincipal section parameters of beams are selected as design variables. A numerical implementation method for continuum DSA is developed by postprocessing analysis results from established finite element analysis (FEA) codes to obtain NVH design sensitivity. The numerical method is tested using large-scale concept and detailed passenger vehicle models. Design sensitivity results are validated using reanalysis results.

The simulation of real world car to pedestrian accidents using a pedestrian humanoid finite element model

Computer models of pedestrian humanoids and detailed vehicle models have been developed to simulate real world pedestrian accidents. The purpose of this modelling is to enable the Ford Forschungszentrum Aachen (FFA) to design, develop and evaluate pedestrian safety technologies under more realistic conditions than the proposed European legislation in order to improve pedestrian safety. LS-DYNA3D has been used to provide an extensive range of modelling possibilities. This paper introduces the humanoid modelling concept created by the FFA, developed by Cranfield Impact Centre (CIC) and being used by the FFA to simulate real world pedestrian accidents. During the initial programme stages the available literature has been used to define the joint, limb and the material characteristics of these models. Whole humanoid verification and validation will be an integral part of the development process.