Abstract
Keywords - Active Vibration Control (AVC), Active Mount, Noise Vibration Harshness (NVH), Car-Body Characteristics, Impedance, Admittance, IFF, Active Damping, Interface
Noise and vibration comfort of modern passenger cars is becoming more important with respect to the customers buying decision and thus to the system design. Because of different improvements during the last decade, even formerly less important noise and vibration sources like the tire-road-contact or airflow excitation gain more attention. Furthermore, also the transfer behaviour dominated by rubber bushings the chassis itself or shock absorbers must be considered when investigating the overall NVH behaviour of the vehicle and its resulting influence on acoustic and vibration comfort.
The presented paper will therefore investigate typical comfort aspects considering low frequency acoustics and related vibrations, so called NVH-characteristics. Several measurements of the transfer behaviour of tire / road induced structure-borne-noise of a vehicle will be discussed and filtering effects of e.g. bushings or chassis parts will be presented to gather the properties of current "passive" solutions. These measurements will focus on impulse-like excitations which appear when driving over bitumen strips or duct cover, but are completed by stochastic excitations caused by rough road surfaces. To reduce especially the impulse like excitations the approach of Active Vibration Control(AVC) using conventional and piezoceramic actuators will be presented. So called active interfaces made of piezo-actuators in combination with passive elastomers will be placed in-between the car chassis and the spring- and damping elements of the under-carriage. A focus of the contribution will be on the description of the interfaces´ working principle, on the design, implementation and testing of the active system itself and on the resulting modifications of the transfer-path properties. The paper will further present experimental results of two "active" solutions for a passenger car in the rear-suspension to assess the impact of AVC on the NVH-behaviour. Additional aspects like cost and required space will be briefly discussed to conclude the overview.