Recent development of road condition estimation techniques for electric vehicle and their experimental evaluation using the test EV "UOT March and I and II"

In this paper, the latest developed results are described about road surface condition estimation for Electric Vehicles (EVs). The road surface condition, represented by "frictional coefficient vs. slip ratio" characteristics, is the most important information for advanced vehicle control, like active safety system. In Hori laboratory, various road surface condition estimation techniques have been proposed using driving-force observer. This observer is based on one of the excellent features of EVs, i.e., motor torque can be known easily and precisely from motor current. First, the principle of the driving-force observer is explained. Next, the road surface condition estimation techniques, μ gradient, μ_peak and λ_opt estimation techniques are introduced. At last, applications of these estimation techniques are shown and confirmed using experimental EVs "UOT March I and II".