# Idle Vibration Reduction of a Diesel Sport Utility Vehicle
## 1 Introduction
For vibration attenuation during engine idling, [PERSON] and [PERSON] [11] developed a non-linear lumped-parameter model of a semi-active engine mount with air springs. To reduce the steering-wheel jitter of a commercial vehicle during engine idling, [PERSON] et al. [12] studied the vibration isolation performance of a powertrain suspension system. In addition, many researchers have attempted to reduce the vibrations of vehicle parts other than engine mounts during engine idling. [PERSON] et al. [13] proposed methods for reducing the transmitted vibration forces caused by the mass unbalance of the radiator cooling fan that occurs during vehicle idling. They demonstrated that the force of vibration of the cooling fan can be reduced by increasing the stiffness of the shroud stators and decreasing the stiffness of the rubber mountings. [PERSON] et al. [14] put forward a half-vehicle suspension model with a double-delay feedback control to improve the vibration performance under idling conditions; the results indicate that the active suspension featuring time-delayed feedback control improved the vibration reduction. Moreover, researchers have explored various methods to reduce the vibration transmitted to the passenger compartment or the steering wheel during engine idling. [PERSON] et al. [15] presented an approach for the active control of a vehicle subjected to harmonic disturbances with time-varying fundamental frequencies. Using this approach, they significantly reduced the sound and vibration levels within the passenger compartment during engine idling. [PERSON] et al. [16] investigated the cause of severe vibration of a vehicle with a four-cylinder engine under engine idling conditions and presented an improved structural design of the vehicle floor to avoid the occurrence of resonance. To reduce the vibration of the steering column during engine idling, [PERSON] and [PERSON] [17] developed an optimal design process for steering column and supporting systems. To improve the overall performances of an automotive steering system, [PERSON] et al. [18] studied the performance of the steering system in terms of steering feel, sensitivity, and modality, and reduced the engine vibration at idle condition. Considering the coupling effect of the multi-source vibration transfer paths, [PERSON] et al. [19] introduced a multi-point iterative analysis method to reduce the total vibration of the steering wheel at idle speed. To solve the vibration problem of an automotive steering wheel under idling condition, [PERSON] et al. [20] proposed a multi-node joint vibration control strategy on the basis of the associated vibration path of the steering wheel. Although several researchers have sufficiently improved the idling engine vibration condition for passenger cars, the vibration from diesel sport utility vehicles (SUVs) remains a matter of dissatisfaction for consumers. To effectively reduce the idling engine vibration of SUVs, a systematic approach, which can clearly analyze the source and transmission path of this vibration using mathematical modeling, is required. In prior studies, researchers have attempted to reduce idling-engine vibrations by targeting specific parts of the vehicle, such as the engine, transmission, mount, body floor, and steering wheel, without considering the entire transmission path of the vibrations. However, not only the aforementioned parts, but also the radiator, intercooler, and front-end module are present in the transmission path of the vibrations; thus, these parts should be considered to reduce the idling engine vibration of diesel SUVs. To the best of the authors' knowledge, studies on the reduction in idling engine vibration, wherein all the parts on the transmission path of the vibration were considered, have not been attempted as yet; this is a challenging task because of the complexity of the connecting structures and supporting conditions of these parts.