The sound level inside an automobile cabin plays a major role in the passengers’ comfort. Active noise control has been widely used to reduce the sound level inside the car cabin. This article presents a design of an active and robust sound control system that can still be efficient despite the changes inside the passengers’ compartment caused by the movement of the occupants. Initially, the coupled acoustic structural analysis is done on a simplified model of an automobile cabin by using finite element and modal coupling methods. Then, the uncertainty of the sound field inside the car, due to the presence of the occupants and the displacement of their heads, is investigated. A multi input multi output robust feedback control strategy, using the H∞ method and considering the unstructured uncertainty of the acoustic structural system, is proposed to reduce the sound pressure level at the ears of all the occupants. In order to achieve performance targets in a broad bandwidth and to reduce the waterbed effect, an optimization is performed on the weight function coefficients. The results show that in the frequency range of 0–334 Hz, the controller has an acceptable performance which is robust to changes in the interior sound field.
In this article, a decentralized strategy is applied for active control of sound inside the automobile cabin by considering the uncertainty caused by the movement of the occupants. A coupled structural-acoustic analysis is done on the simplified geometry of the automobile cabin with passengers by the finite element method. The uncertainty caused by changes in the occupants’ head positions and angles is also considered. Then, a decentralized robust feedback control strategy is proposed to reduce the sound pressure level in the ears of all the occupants using the H∞ method for each individual control unit by considering the unstructured uncertainty of the plant. The efficiency of the proposed control strategy in minimizing the sound pressure level caused by the structural disturbance on the firewall panel is investigated.
Osseointegrated dental implants are deficient in natural periodontal ligaments. It may therefore, disrupts the natural function of implant and leads to excessive stress and strain in jaw bone. Our new proposed implant has the nonlinear internal component which imitates periodontal ligaments function. A nonlinear finite element analysis developed to investigate the efficiency of utilizing this nonlinear internal layer for three conditions of bone implant interface conditions under vertical and horizontal loading conditions. Our results so far indicate that the use of a class of material exhibiting incompressible hyperelastic behaviour as a internal layer can reduce the peak stress deduced from different loads. The mobility of implant supported prosthesis is similar to that of natural tooth and micromotion at the bone-implant interface is decreased for both delayed and immediately loading treatment.
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