Full Vehicle Multi-body Model Research Articles

EVs on Road Ground-Impact Energy Evaluation Methodology: Dynamic of a Finite Element (FE)-Based Battery Pack Integrated into Full Vehicle Multi-Body Model on Abaqus

<div class="section abstract"><div class="htmlview paragraph">The present paper documents a comprehensive study on the ground-impact of battery packs in Electric Vehicles (EVs), a paramount concern for vehicle manufacturers. During an accidental crash, battery packs are usually exposed dangerously to possible intrusion of foreign objects (e.g., road debris). With the purpose of developing a generic methodology to evaluate the released energy content and due to high nonlinearities involved during the ground-impact maneuvers, a hybrid full vehicle model is needed. Hence, both FE-based battery case and virtual energy sensors have been integrated into the current Abaqus multi-body (MB) full vehicle model (suspensions, steering system, engine and a trimmed body). Energy peaks are estimated simulating a vehicle going over obstacles that a typical customer can encounter in daily-life (no off-normal situations) performed at different approaching speeds and obstacle sizes.</div><div class="htmlview paragraph">To evaluate the energy, the battery plate is divided as if it were a spaced grid of identical square-sized modules. Plate surface modularization is useful to install properly a certain amount of virtual sensors that store and measure the energy released during the impact. In addition, this strategic layout promotes the accuracy of the contact conditions between obstacles and the battery case.</div><div class="htmlview paragraph">The concept underlying the proposed multidisciplinary sequential procedure, based on three different phases (on road-impact energy evaluation, load cases definition and battery case/mechanical structure strength), ensures both to define specification for subsequent analyses (making iterations on the structure faster) and to possibly complete an effective design validation of the specific vehicle project under test. This methodology has been successfully applied transversally to several vehicle architectures (e.g., light commercial vehicles, sport/compact utility vehicles, supercars) and it shows the benefits of choosing the integration strategy over a typical co-simulation approach.</div></div>

Parameter optimization for a vibration attenuation system on ambulance stretchers

In this work a parameter optimization method is applied to determine the best values of damping and stiffness properties which will minimize the magnitude of the vertical acceleration of the ambulance stretcher. Thus, an 8-DOF vehicle dynamic model was developed to be used for the parameter optimization method. Subsequently, the results obtained by the model were compared to a full vehicle multi-body model of Carsim software. Damping and stiffness properties, which are obtained by a parameter optimization method, contribute to reducing the magnitude of the vertical acceleration of the ambulance stretcher. The approach developed in this study provides sources for designing a mechanism to reduce the vertical acceleration to which the patient is exposed during transportation in an ambulance.

The influence of bicycle fork bending on brake control

Bicycle forks are prone to bending, introducing a flexible structure between front wheel and vehicle body. This has substantial influence on brake control, not only by altering the system dynamics but also causing serious estimation problems. These consist in considerable measurement errors in the incremental wheel speed and longitudinal tyre velocity signals, both affecting the wheel slip estimation. This paper provides an in-depth analysis of this problem that represents a profound difference to classical vehicle dynamics. For this purpose, measurements are recorded in test manoeuvres using an extensive set of measurement variables. Based on this data, the complex nonlinear couplings of longitudinal and vertical dynamics are included in a full-vehicle multibody model. The measurement errors as well as compensation methods are evaluated using both simulation and experimental data. In order to examine the influence on closed-loop brake control a linear control-oriented model is derived. Finally numerical full-vehicle simulations show the influence of fork bending on discrete anti-lock brake control systems (ABS), distinguishing the sheer dynamic phenomenon and the related estimation problem.

A methodology to assess frontal stiffness to improve crash compatibility

Improved crash compatibility for vehicles is the next step towards increased frontal impact protection. Two aspects of crash compatibility are frontal stiffness and mass. Currently, frontal stiffness is related to mass and heavier vehicle tend to be stiffer than lighter ones. Consequently, the risk of being over-crushed in frontal impacts increases with mass-ratio. This study investigates one methodology to match frontal stiffness levels for vehicles in frontal impacts with different mass ratios. A generic, full vehicle multi-body model is used, the frontal stiffness properties of which are obtained from one full width crash test and one offset crash test. A small vehicle fleet has been developed using this methodology. The study shows one possibility for developing generic vehicle models that can be used to match frontal stiffness levels for vehicle with different masses.