Car Simulacion

Safety and Reliability of
Distributed Embedded Systems

Technical Report ESL 04-01

Simulation of Vehicle Longitudinal Dynamics

Michael Short
Michael J. Pont
and
Qiang Huang
Embedded Systems Laboratory
University of Leicester

[ESL04-01A - 11 OCTOBER 2004]

Project summary
This technical report is one of a series (listed in full below). Together these reports describe acomplete hardware-in-the-loop (HIL) simulation that reproduces the behaviour of a passenger car
travelling down a motorway. In the simulation, the speed and position of the car are determined
by an adaptive cruise control system implemented using one or more embedded microcontrollers.
The test bed is intended to be used to assess and compare different software architectures for use
in distributedembedded systems, particularly those for which high reliability is a key design
consideration.

Full list of reports in this series
Available now:
ESL04/01 “Simulation of Vehicle Longitudinal Dynamics”
ESL04/02 “Simulation of Motorway Traffic Flows”
ESL04/03 “Development of a Hardware-in-the-Loop Test Facility for Automotive ACC
Implementations”

Forthcoming:
ESL04/04 “ControlTechnologies For Automotive Drive-By-Wire Applications”
ESL04/05 “10-Node Distributed ACC System: Co-Operative Implementation”
ESL04/06 “10-Node Distributed ACC System: Pre-Emptive Implementation”

Acknowledgements
The work described in this report was supported by the Leverhulme Trust (F / 00212 / D)

[ESL04-01A.DOC - 11 OCTOBER 2004]

Contents
1.

Introduction............................................................................................................1
1.1
The Two-Wheel Traction Model....................................................................1
1.2
System Block Diagram...................................................................................2
2. Equations Of motion..............................................................................................3
2.1
Vehicle load distribution ................................................................................3
2.2
Drag forces .....................................................................................................4
2.3
Tractive properties of the tyre/road interface .................................................4
2.4
Wheel dynamic equations..............................................................................6
3. Powertrain Model ...................................................................................................8
3.1
Engine torque curve .......................................................................................8
3.2
Engine dynamics..........................................................................................10
3.3
Gearbox model .............................................................................................11
4. Brake System Model ............................................................................................12
4.1
Servo actuated brake system ........................................................................12
4.2
Brake friction characteristic.........................................................................13
5. Parameter Selection ..............................................................................................14
6. Simulation Results................................................................................................15
6.1
Acceleration Performance............................................................................15
6.2
Braking Performance....................................................................................16
7. Conclusions ..........................................................................................................17

[ESL04-01A.DOC - 11 OCTOBER 2004]

1. Introduction
This document describes the development of a model of the longitudinal dynamics of...