Integrated Approach for NVH Engineering of Low Weight Vehicles Chassis
In general terms the result of the project is the development and validati on of an integrated simulation environment that can be used for the system analysis of vehicles for noise, vibration and harshness (hereinafter NVH) prediction and refinement. The driving idea was to create a coherent simulation environment where all the subsystems and components, described by numerical models or by experimental characteristics, could be assembled in a vehicle virtual prototype, systematically analysed and optimised on a realistic mission profile. The INVEC project developed the numerical and experimental enabling methods and tools and demonstrated the feasibility of such an integrated approach on typical test cases, consisting in the system analysis of innovative vehicles. The added value can be evaluated on two aspects: the range of validity of the methods and the suitability for application. Regarding validity all the building blocks needed to perform the system analysis of a vehicle for NVH purposes were improved. The simulation models of the components (shock absorbers, bushings, hydromounts, tyres studied in collaboration with Monroe, Paulstra, Freudenberg and Pirelli) improved their range of validity. Methods for simulating vehicle structures, body frame and sub-frames, taking account of real characteristics of structural flexibility either provided by a Finite Element model or by an experimental characterisation were developed and validated. In particular an original method was developed to enable the simulation of flexible structures characterised entirely by vibration tests. The target frequency range 0-200 Hz was reached for most components. The validity of full vehicle simulations, verified directly by the partners on test cases, was extended to a frequency range where the vehicle response is strongly affected by structural response, without paying unacceptable drawback in terms of simulation cost. Regarding suitability for applications, the research activity carried out in INVEC gave results in two directions: 1. Pushed the development of simulation and testing capabilities of the single components 2. Created the conditions for a wider applicability into the vehicle development process. The Multibody models of the components were developed in view of the application in a co-design process of vehicle refinement. For components such as hydromounts and bushings original identification procedures were developed to obtain the parameters of the simulation models from characterisation tests. A multi-objective numerical optimisation procedure to be applied on a full vehicle model on a typical NVH mission profile was developed.