Adaptive Road Noise Control

Vehicle Dynamics without Compromise

Colin Peachey Lotus Engineering

04/22/082

Overview

• Modern vehicle suspensions balance refinement (isolation) and dynamics (control).

• OEM’s frequently compromise dynamics to keep refinement acceptable (and vice versa).

• Active noise control (ANC) was developed by Lotus to reduce low frequency noise inside the vehicle cabin by generating an opposing sound field through the audio system.

• Using ANC the level of compromise can be reduced and the vehicle optimised for dynamics with less regard for roadnoise asthe NVH problems can be resolved using active technology.

04/22/083

How Sound Balance in cars has changed

60

65

70

1994 2004

RoadnoiseEnginenoisewindnoise

• Roadnoise has increased • Engine noise has decreased• Windnoise has marginally

decreased

• Roadnoise is now dominant sound when cruising.

• Engine noise conveys purpose / power & provides driver feedback for gear change etc..

• Roadnoise is just fatiguing and annoying and has zero purpose or benefit.

Lotus Data – C segment model

04/22/084

Why is Roadnoise increasing?

225/45W17Volkswagen Golf V. GTi195/65H15Volkswagen GOLF V195/65V15Volkswagen Golf IV. 1.8 GTi175/80T14Volkswagen GOLF IV185/60H14Volkswagen Golf III. 1.8i GT175/70T13Volkswagen GOLF III185/60V14Volkswagen Golf II. Gti155/80T13Volkswagen GOLF IIStandard Tyre SizeModel

Universal trend for wider low profile tyres

Example of VW Golf

04/22/085

Suspension inputs increasing

Multi link suspensions create multiple noise paths into the vehicle.

Bushes are harder for improved handling capability reducing isolation levels.

04/22/086

Adaptive Road Noise Control (ARNC)

Engine Sound Synthesis

Engine Order Cancellation (EOC)

Lotus ANC technologies

850 44001000 2000 3000 40001200 1400 1600 1800 2200 2400 2600 2800 3200 3400 3600 3800 4200

rpm

30

80

40

50

60

70

35

45

55

65

75

33

38

43

48

53

58

63

68

73

78

dB(A

)Pa

F Overall level Driver_DX (A) Runup_neutral_OFFF Overall level Driver_DX (A) Runup_neutral_ONF Order 2.00 Driver_DX (A)F Order 2.00 Driver_DX (A)

reduction in overall noise

reduction in 2nd

order engine noise

04/22/087

Principle of Noise Cancellation

ANC output

Vehicle noise

Resultant Noise Phase

correct

Cancellation

Phase incorrect

Noise increase

04/22/088

Schematic of Lotus RNC System

Loudspeaker System

(Common with Audio)

Error Microphones

(Feedback adaption)

Adaptive Controller

Accelerometers –(feedforward reference)

04/22/089

Frequency range of Active Control

250 Hz

PASSIVE RANGE

(Sealing and absorption treatments)

Frequency

ACTIVE RANGE

(Conventional treatments are mass and stiffness)

0

System off

System on

04/22/0810

Example of system benefits

• Two European premium sector luxury saloons were tested.• Comfort Car – premium brand high comfort and refinement RWD

– Limited to 250 kph– Tyres: Front 255/45/18 Rear 275/45/18

• Dynamics Car – premium brand sports saloon 4WD– >300 kph maximum speed.– Tyres: 275/40/19

• Both cars were rated subjectively on 1 to 10 scale for all aspects of driving dynamics and comfort and measured for interior noise.

• The Dynamics car was then fitted with the Lotus Active Roadnoisesystem and re-measured.

04/22/0811

Overall Vehicle Dynamics Performance

6

6.5

7

7.5

8

8.5

9Steering Response

Steering Connection

Handling - CorneringIsolation

Road Noise

Dynamics Car

Comfort Car

04/22/0812

Dynamics Car 1 Vs Comfort Car 2

• Base cars no ARNC, Coarse Chip Road 80 km/h

LHF RHF

RHRLHR

04/22/0813

Dynamics car with ARNC Vs Comfort car

• Dynamic car with ARNC , Coarse Chip Road 80 km/h

LHF RHF

RHRLHR

04/22/0814

• ARNC Comparison, Coarse chip Road 80 km/h

Dynamics car ARNC Off ARNC On

LHF RHF

RHRLHR

04/22/0815

Noise influence on “isolation feel”

• The subjective “isolation feel” is created by the combined noise and vibration response experienced by the driver.

• Reduced noise response generally creates a more favourable isolation impression even if vibration is unaffected.

• However to maximise vibration isolation the steering column and seat needs to optimised for vibration transmission.

• This is easier to do if the constraint of roadnoise isolation has been reduced as a development priority.

• In addition stiffer suspensions will have better yaw stability which benefits steering response :- hence very rigid rack mounting stiffness may not be essential.

04/22/0816

Effect of Impact Strip – isolation improvement

Impact response – RHR noiseARNC Off

ARNC On

04/22/0817

Impact strip noise – Effect of ARNC - detail

RHR Seat ARNC Off RHR Seat ARNC OnFr

eque

ncy

30 –

450

Hz

Freq

uenc

y 30

–45

0 H

z

04/22/0818

ARNC- Smooth to rough transition response

ARNC Off ARNC On

04/22/0819

Overall Vehicle Dynamics Performance

6

6.5

7

7.5

8

8.5

9Steering Response

Steering Connection

Handling - CorneringIsolation

Road Noise

Dynamics Car

Comfort Car

04/22/0820

Overall vehicle Dynamics Performance – with ARNC

6

6.5

7

7.5

8

8.5

9Steering Response

Steering Connection

Handling - CorneringIsolation

Road Noise

Dynamics Car

Comfort Car

04/22/0821

• Landstrom and Landstrom (1985) showed low frequency monotonous noise and vibration increased drowsiness levels.

• Loftstedt and Landstrom (1987) showed truckdrivers become more readily fatigued driving trucks that generated high levels of low frequency noise.

• ROSPA (2001) have shown 20% of UK road accidents are fatigue related.

Noise contributes to accidents

04/22/0822

Further Applications of Lotus Active noise technology

• The range of ANC technologies can also be applied to realise other specific benefits.

• CO2 reduction– Vehicle weight reduction– Extended operation of engine cylinder deactivation– Maintain refinement with engine balancer shaft deletion

• Reduced programme costs– High end Halo models from high volume platforms– Reduced development time for derivative models– Increased product differentiation from common platform strategy

• Improved customer feature– Improved dynamics– Improved refinement– Enhanced driver enjoyment (sound synthesis) – Pedestrian safety for electric and hybrid vehicles

04/22/0823

Summary

• Roadnoise is now the dominant NVH problem in a majority of vehicles.• Refinement and vehicle dynamics requirements are often in conflict

requiring compromise (NVH is usually the victim).• ANC is a viable solution to low frequency noise in vehicle interiors

which can negate much of the conflict.• The system can have a dramatic effect on vehicles with high levels of

low frequency structural noise.

• This technology can be exploited to achieve class leading dynamics and refinement on the same vehicle – and achieve vehicle dynamics without compromise.

• The technology is available now and we are already working with a number of potential suppliers of the production solution.

04/22/0824

Further information

For further information on the full range of Lotus active noise technologies please contact:-

Colin Peachey - Chief Engineer NVHLotus EngineeringHethel NorwichNorfolkEnglandNR14 8EZ+44 (0)1953 608926E mail cpeachey@lotuscars.co.uk

Or go tohttp://www.grouplotus.com/engineering/products_services.html