Results from the test track in the eVALUE project

Fredrik Bruzelius, Mattias Hjort, Håkan Andersson

Fredrik BruzeliusResearcher – Vehicle technology and Simulation (FTS) @ the Gothenburg office

Main interestsVehicle dynamics, vehicle modeling, tire modeling, active safety functions; testing, classification and performance

Ongoing/planed projects•Classification of winter tires, ”what is a winter tire?”•ESC performance on slippery surfaces and the interaction of tire characteristics•Vehicle models for driving simulators•Chassis-tuning in driving simulators

Academic backgroundMSc in Applied Mathematics, PhD in Automatic Control

The eVALUE Project Overview

● An EU seventh frame program project● Eight partners all over Europe● Started in January 2008 and ended in December 2010● Over all budget of 3.76 M€

Project objectives/motivation

Active safety is a key measure when it comes to decreasing traffic accidents, injuries and deaths.

Active safety functions are introduced into new vehicles, so far only in premium vehicles.

However, and in opposition to passive safety, the car buyer cannot judge the performance of a vehicle’s active safety based on objective measures.

Every vehicle OEM is promoting active safety, but mainly on functionality rather than on safety impact.

Need for objective test methods for active safety!

Promote active safety by increase the public awareness through a test program (c.f. NCAP)

Support the development of active safety functions

The approach

Accidents

Relevant scenarios

Testing & Evaluation Methods

Safety Impact

Step 1

Inspections

Step 2

Physical Testing

The approach continued

Scenario based testing

+

Holistic vehicle perspective

● The subject vehicle (target of the test) is treated as one unit

● No function in particular is regarded● The vehicle performance in the

measured, and relates to traffic safety impact via a Safety Performance Indicator

● Simpler to grasp the point for the end customer: How did the vehicle perform in that critical situation?

● Simpler updates, driven by accident statistics rather than the technical development of functions

● Etc, etc

Selected scenarios

Not driven fully by accident statistics due to lack of available information in present databases.

Future databases looks promising to be used in this context. Chosen from common sense, OEM practice, statistics to the

extent there is information Three groups of scenarios

Longitudinal scenarios Lateral scenarios Stability scenarios

Addressing (implicitly) most of the present functions available on the market today as well as at least near future functionality

Selected scenarios: Longitudinal scenarios(rear-end collision situations)

Straight road

Subject vehicle

Target vehicle vt

at , vt

Subject vehicle Target vehicle

Wt

at , vtas, vs

Subject vehicle

Target vehicle

vtvs

Curved road

Transversally moving target

Selected scenarios: Lateral scenarios(Lane/road departure situations, no high slip)

vt

vt

vs

vs

vs

R

vs

R

Subject vehicle

Target vehiclevt

vs

Lane and road departure on a straight road

Lane and road departure on curve /

on a straight road just before a curve

Lane change collision

Selected scenarios: Stability scenarios(high slip situations)

vs

vs

High µ

Low µ

High µ

Low µ

amax

amax

vs

Wt

vs

vs

R

R

R

vs

Emergency breaking on split surfaces

Obstacle avoidance

Highway exit

Development tests: Highway exit

Novel test maneuver tests performed at test track in Germany

(ATP) Steering robot (developed by VTI/Autoliv) to

execute the maneuver with a pre-defined steering wheel angle trajectory (open loop)

Suggested steering normalization: single point characterization adopted from the NHTSA FMVSS126 (sine with dwell)

Suggested measure (Safety performance indicator) is the “ending” vehicle radius

Proposal: Use nonlinear steering geometry characterization and traveled distance in lane as a performance indicator

-80 -60 -40 -20 0 200

10

20

30

40

50

60

70

80

90

Development tests: split surface braking

Standard procedure among OEMs and suppliers as a development test (performed in closed loop)

Steering wheel locked (steering robot) during panic braking (open loop)

The force difference between the two vehicle sides due to the surfaces creates a yawing torque on the vehicle and consequently a yaw motion

The performance trade-off is stability (straight course following) versus stopping distance

A performance index have been developed and tested in field that consider the trade-off and normalizes the tire to road friction.

Development tests: rear-end collision scenarios

Standard test procedure at OEMs and suppliers for development purposes

Rear end collision tests with dummy (balloon car) performed at different locations

No moving target tests performed. Difficult task of synchronization.

Braking robot used to achieve repeatability and reproducible results

Braking robot initiated by the warning from the vehicle

Sound, haptic and light warnings can be sensed and used in the robot trigger application!

Collision speed as the strongest candidate for a performance index

0 0.5 1 1.5 2 2.5

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Time (s)

Sen

sor

sign

al (

V)

FCW induced robot braking on static target

4 bar: rear pos

2 bar: rear pos3 bar: rear pos

4 bar: front pos

Open issues

How many repetitions is sufficient? Is it determined by the uncertainties of the test method?

How to incorporate the drivers response to the assessment? Is it possible at all? Does it make sense? Is a isolated HMI test sufficient? Closed loop testing is infeasible/impossible!

How to handle missed warnings/interventions? This has a huge impact on the traffic safety and needs to be assessed!

How to handle false warnings/interventions? This might not be as bad as missed warnings for traffic safety but will effect the credibility of the function.

How to ensure that the test environment resembles real world situations? For example, how to ensure that dummy vehicles are detected in a similar manner as a true vehicle by the functions sensor.

Conclusions

Deriving a testing program for active safety is non-trivial! The concept of scenario based testing with a holistic vehicle

view point is sound an proven to work. The concept have been adopted by more recent initiatives (vFSS, ASSESS etc)

Much work remains● Performance indices needs to further developed and establish a

link to a real traffic performance.● Further development of environment, e.g. dummy vehicles,

synchronization between tested vehicle and dummy vehicle etc. etc.

● Further establish repeatability and reproducibility of the test results for different settings; test tracks, test conductors, tires etc. etc.

● Establish acceptance and credibility among OEMs, suppliers and finally car-buyers

Thanks for your attention!