Objectives and content
The comfort of the occupants is one of the major objectives of automotive design. Among the various aspects that form the overall perception of comfort in a vehicle the isolation from noise and vibration is particularly important because it affects also the drivers efficiency. Today every car manufacturer has developed and uses methodologies for the NVH (Noise, Vibration, Harshness) analysis and testing that have substantially contributed to the improvement of the NVH performances of the European vehicles in the past years. Many research activities are actually running aiming at further improvements of these methodologies and some of them under E.C. funding.
The new scenario of Low Weight Vehicles (in view of the strict emission, fuel consumption and noise constraints arising in Europe, Japan and US) creates the need for a substantial step forward. The long term aim of cutting down the fuel consumptions at one third of the actual values (that means a weight reduction from 20 to 40% according to PNGV in the US or to EUCAR Master Plan in Europe), while meeting the same levels of customer satisfaction pushes towards innovative design solutions and methodologies tackling new challenges such as the following:
- elimination of traditional trade-offs between NVH and weight such as structural reinforcements and fittings
- isolation of increased levels of road induced vibrations due to low rolling resistant tires
- use of innovative materials and technologies for vehicle structures for which there is limited experience, knowledge based design criteria and engineering data bases
- reduction of lead time and prototyping constraints.
The need for new design approaches for the NVH of the Low Weight vehicles originates then from the impossibility to rely on carry over that means not to rely on the solid baseline that still constitutes the 80% of the car design know how and on which the existing design methodologies are modelled.
The envisaged new approaches are based on accurate system analysis in which the subsystems and components are systematically analyzed, tested, coupled together and finally evaluated and optimized on a realistic mission profile through Multiobjective Design Optimization.
The objective of the proposed research is to develop the tools and to demonstrate the feasibility of such approach for the NVH engineering of innovative vehicles. The building blocks of the proposed approach are the development of new algorithms enabling features such as flexible vehicle simulations coupling suspensions to synthetic models of the car body response coming from numerical models or from experiments, the simulation of a complex NVH mission profile and the construction of a novel Multiobjective Design Optimization process to optimise the suspensions parameters on the mission profile.
The feasibility will be demonstrated on conventional vehicles in order to allow for an adequate validation and sharing of the methodology results and on innovative vehicles such as ZIC (FIAT) and MOSAIC (RENAULT) to assess the suitability to Low Weight Vehicles tasks. The application to existing vehicles and related technologies, instead of more theoretical and simplified test cases, originates from the need to assess the methodologies on physical products containing the innovative materials along with all the technical and technological features that make the real car. The new algorithms developed for the improvement and the integration of the computational and experimental methodologies will maintain a general validity and could be easily extrapolated to other application fields.
Funding SchemeCSC - Cost-sharing contracts