# Idle Vibration Reduction of a Diesel Sport Utility Vehicle
## 1 Introduction  
In recent years, as enhancement of the driving experience and comfort of consumers become paramount, the reduction in vibrations in vehicles during engine idling has garnered significant research attention. The vibration during engine idling is transmitted from an operating engine to a passenger while a vehicle is stationary, which significantly influences the buying preference of consumers. The vibrations during engine idling are clearly perceived by passengers, which, when large, negatively impacts the passengers' impression of the vehicle. Such vibrations are dominated by low-frequency components and differ from those caused by road and wind perturbations during driving. Moreover, because compression-ignition-type diesel engines bear a substantially higher compression ratio than spark-ignition-type gasoline engines, diesel engines exhibit remarkably larger vibrations during engine idling than gasoline engines. Accordingly, various methods have been studied extensively for the reduction in vibration in diesel vehicles during engine idling. Fundamentally, the vibration occurring during engine idling can be reduced by minimizing the vibration of the engine and transmission, which act as vibration sources during engine idling. To this end, several researchers have reported on related and relevant topics. [PERSON] et al. [1] proposed an engine-transmission control approach to improve fuel economy during urban driving and reduce the engine vibrations transmitted to the passenger compartment. [PERSON] and [PERSON] [2] introduced two intelligent control systems to reduce the fluctuations in engine speed in idle conditions, namely an evolutionary computingcontrol based on genetic algorithms and a stochastic control based on the Alopex algorithm. [PERSON] et al. [3] proposed a hybrid proportional electromagnetic dynamic vibration absorber comprising an electromagnetic actuator and an elastic element to control the engine vibration during idling. Moreover, [PERSON] et al. [4] presented an experimental study on the first-order vibration improvement of a malfunctioning vehicle in development during the engine idle condition. They analyzed the generation mechanism of the first-order vibration problem during engine idling, and subsequently, experimentally derived the possible vibration excitation source and transfer path. Recently, several studies have been conducted to reduce the vibration caused by the gear rattle in the transmission during idling [5; 6; 7; 8; 9]. [PERSON] et al. [5] proposed a nonlinear torsional model of a driveline system to study the gear rattle during idling and advanced a design guideline for the selection of adequate clutch stiffness and damping properties of the clutch to reduce gear rattle. [PERSON] and [PERSON] [6] employed an analytical model featuring a new time-varying gear mesh stiffness function to investigate the influence of the clutch disk mechanism on the rattle during engine idling. Based on the magnetorheological effect in elastomeric spring elements, [PERSON] et al. [7] developed a device housing a flywheel equipped with a torsional vibration damper, which can reduce the gear rattle of the flywheel in a low-speed regime. [PERSON] et al. [8] conducted a study to reduce the vibration of a dual-mass flywheel torsional damper under multiple working conditions including ignition, idle, startup, and drive conditions. Excluding the engine and transmission, the vibration of vehicle components situated along the vibration path during engine idling have been minimized in numerous research. Among these studies, the studies related to mount structures have been most actively conducted. [PERSON] and [PERSON] [9] proposed a magnetorheological engine mount for the vibration control of a vehicle and evaluated the vibration at the driver's position in the time and frequency domains. [PERSON] et al. [10] introduced a new engine mount with variable stiffness, which provides superior vibration control over that of a hydro-mount and a passive rubber mount under idling conditions.