Optimal control of hybrid electric vehicles by considering engine and tire/road noises

Along with exhaust emissions and fuel consumptions (FCs), noise emission from cars is one of the main concerns of the automotive industry. Hybridization is a promising method not only to make automobiles more environmentally-friendly, but also to reduce their noise emissions. However, a proper control design for hybrid electric vehicles (HEVs) to make noise emissions lower is still required in addition to exhaust emissions and FC reductions. In this study, we modify Equivalent Consumption Minimization Strategy (ECMS) to keep the engine noise less than tire/road noise during driving. A test bench is established for calculating the engine noise and brake specific fuel consumption. Moreover, the tire/road noise is experimentally defined as a function of the vehicle speed. It is shown that implementing the basic ECMS, the engine noise exceeds the tire/road noise in some moments of driving cycle, which is annoying to the passengers. Therefore, a modified ECMS is proposed to limit the candidate engine operating points such that the engine noise does not exceed the tire/road noise. It is shown that the engine noise level is kept below the tire/road noise level by using the modified ECMS at the expense of a very small increase in the vehicle’s FC.