Research on speed raise curve of hybrid electric vehicle during acceleration process based on optimal efficiency

If driving system structure and parameters of hybrid electricity vehicle(HEV) are determined, then HEV´s energy saving potential depends on the control strategy. Traditional control strategy didn´t take HEV´s speed raise curve into account during vehicle´s accelerating process, so engine and motor can´t work at optimal efficiency work point at the same time. In order to improve HEV´s efficiency, with a kind of reverse thinking, the paper analyses the optimal efficiency work curve of engine and motor, then puts forward the method about how to get HEV´s perfect speed raise curve by utilizing the optimal efficiency work curve of engine and motor, and the curve is got. It can be shown from the simulation results that HEV´s perfect speed raise curve makes both engine and motor working at optimal efficiency work point simultaneously during HEV´s speed raises from 0 to 4.166m/s (15km/h), and the energy consumption is lowest. Comparing to speed curve of New European Driving Cycle working condition, this curve can lower engine´s fuel consumption by 4.82% and improve motor efficiency by 5.55%.