Optimization Approach to Passive Engine Mounting System for Reducing Automotive Vibrations

Improvised noise, vibration, and harshness (NVH) performance of vehicle implies better comfort for passengers. Apart from road inputs, engine vibration is one of the major contributors to interior vibrations in automotive. The aim of this paper is to optimize specifications and locations of engine mounts to reduce vehicle vibration without affecting engine performance and to provide better ride comfort. This paper also includes the challenges involved in the analysis of engine vibration on critical conditions such as movement on the road surface or braking action. Therefore, a fully numerical simulation expands to a four-cylinder engine by considering piston side force. In this model, the mass distribution in the connecting rod and crankshaft, outside of the center pin, and friction between the cylinder and piston have been considered. Furthermore, simulation analysis is implemented for an engine in vehicle movement with constant speed on the road class B roughness and braking conditions. Engine location, the angle of placement, and dynamic characteristics of mounts are the important parameters to reduce vibrations transferred to the vehicle frame. The optimization of these parameters is carried out using one of the most promising heuristic multi-objective optimization methods, genetic algorithm (GA) process. The new combination of optimal mount system variables in comparison with baseline configuration showed that the root mean square (RMS) value of vehicle displacement declines up to 47 percent in the engine operating range. In addition, the resonance frequencies thereof change and occur at lower than idle engine speed. Achieving remarkable reduction of vibration was confirmed on the vehicle showing that this optimization is effective in reducing vibration.