Improvement of Quietness in the Cabin by Engine Control based on Road Noise Estimation for New Series Hybrid System

Engine start timing of series hybrid system is important for quietness in the cabin and comfortable because its engine operation timing is not restricted by vehicle speed and acceleration. There is an opportunity to operate the engine without spoiling quietness if engine sounds could be covered by road noise. Discovering the correlation between road noise and variance of wheel angular acceleration using wheel speed sensor made it possible to estimate road noise. Engine start control based on this road noise estimation algorithm contributes to cabin quietness performance improvement as the result of less frequency of engine operating during smooth road driving.