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Modelling For Competitor Vehicle Analysis

By Martin Ljunggren and Gunnar Sahlin

Abstract

This thesis describes the development and evaluation of a competitor vehicle model for Volvo Cars Corporation's moving base driving simulator. Vehicle simulations are important when aiming for decreased development time within the vehicle industry. Simulations help the engineers to front-load projects, thereby improving efficiency and product quality. To remain competitive it is essential to know the industry's state of the art technology. One commonly used method is competitor analysis. The thesis delivers a method of how to measure a competitor's vehicle in order to create a vehicle model that can be tested objectively in VI-CarRealTime as well as subjectively in a driving simulator. This gives the opportunity to save the competitor vehicle in a database and perform tests even if the physical vehicle is no longer available. The thesis focuses mainly on capturing the lateral tyre and steering characteristics of the competitor vehicle with the main priority to mimic the full vehicle behaviour while minimising additional requirements needed compared to a standard measuring. It is favourable to separate the different system in the full vehicle model in order to facilitate the vehicle analysis on component level. Two methods are presented and carried out. One named Measurement Based Method that requires measured tie-rod forces using strain gauge sensors on the tie-rods as an additional measuring equipment. The second method named Estimation Based Method is using the standard measuring equipment but instead requires a Brush Tyre Model to correlate lateral tyre characteristics to aligning torque. The advantage of knowing the tie-rod forces is that tyres and the steering system can be completely decoupled from each other which gives higher accuracy on component level. The tyre model is optimised so that the simulated vehicle shows the same response as the measured vehicle in a series of manoeuvres. The lateral tyre parameters are assumed to be found when the vehicle model is achieving the same yaw rate and lateral acceleration as for the physical vehicle in an identical manoeuvre. A steering algorithm is designed to imitate the behaviour of vehicle's power steering system by estimating the relation between rack force and steering wheel torque. The resulting steering algorithm is tuned to simulate the wanted steering system by adjusting damping and friction parameters together with a base torque given by a velocity versus rack force dependent look-up table. Objective evaluations show good correlation for low transient manoeuvres. However, at higher transients the tuned models differentiated more from the measured data. The Measured Based Method was thought to have higher accuracy when evaluating subjectively which resulted in it to become the favourable method. Further work needs to be carried out on both the steering system and the tyre optimisation in order to have an established method

Topics: Vehicle model, Competitor vehicle, VI-CarRealTime, Volvo Cars, Driving simulator, Vehicle dynamics, XC90, Tyre parametrisation, Torque feedback
Publisher: Chalmers University of Technology, Göteborg
Year: 2016
OAI identifier: oai:publications.lib.chalmers.se:239092
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