Postgraduate Dissertation


Driver Model Development for Lateral and Longitudinal Control at the Limits of Handling

Abstract

This dissertation describes modelling of a human driver with a computer simulation that is capable of responding to the mathematical path information. The steering output produced by the driver model is integrated into a 2DOF vehicle dynamics model that is validated with a multi-body dynamics model for a step-steer input. The path information describes a smooth curvature with the application of a sigmoid function. The path represents the driver’s intent to avoid an obstacle with a single lane-change manoeuvre. Considering that the desired path is known, the driver model in this dissertation focuses on tracking the path with minimum tracking errors. The driver model controller is divided into two levels. The first level is an upper-level controller that is designed to determine the desired front lateral tyre force using feedforward-feedback controller. To calculate this front lateral force, the feedforward part uses the vehicle centre of percussion (COP) about the rear tyre. The concept of COP is selected to eliminate the dynamics of the rear tyres and simplify the feedforward part. The feedback part uses the set of steering gains from lane-keeping steering with the yaw-damping effect to provide path tracking stability. The second level is a lower-level controller which calculates the steering wheel angle using the desired front lateral tyre force from the upper-level controller. The simulation results show that the driver model robustly tracks the desired path and reduces the lateral and yaw error between the vehicle trajectory and the reference path by a minimum of 20%. The results highlight the effect of steering gains and vehicle longitudinal speed on the path tracking ability of the vehicle. The vehicle uses a tyre model to consider the non-linear behaviour of tyres for accurate model results. In addition to the single lane change track, the driver model executed its ability to operate in a vehicle overtake environment by driving along the reference path with a double lane change manoeuvre. The performance of the developed driver model is explored to study the controller’s ability to drive understeer, neutral-steer or an oversteer vehicle ensuring tracking ability and stability. KEYWORDS: Driver model, lateral controller, sigmoid function, path tracking, vehicle dynamics.



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Authors

Maity Rahul

Contributors

Rights Holders: Maity Rahul
Supervisors: Ferreira Miguel

Oxford Brookes departments

School of Engineering, Computing and Mathematics

Degree programme

MSc Automotive Engineering with Electric Vehicles

Year

2020


© Maity Rahul
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