Future vehicle society based on electric motor, capacitor and wireless power supply

Future electric vehicles (EVs) will be linked to the electric power system infrastructure; the vehicles will operate through frequent electric charging, as is the case with electric trains. Conventional batteries require a long recharging time; therefore, supercapacitors, rather than batteries, will play an important role in the future for charging of EVs. Recently, we manufactured small EVs powered only by supercapacitors. Supercapacitors have a long operating life, large current density, and environmentally friendly composition. Further, their energy level can be estimated from their terminal voltage. Because EVs powered by supercapacitors can operate for more than 20 min after being charged for only 30 s, the requirement for constant recharging of EVs is reduced substantially, thereby increasing the efficiency of these EVs. Wireless power transfer based on magnetic resonance is an extremely important technique that needs to be considered for enhancing the efficiency of EVs. In a laboratory experiment, this technique enabled approximately 50 W power transfer with more than 95% efficiency at a distance of more than 50 cm. In order to improve energy efficiency and safety of future EVs, the implementation of novel motion control techniques for EVs is required. Since EVs are powered by electric motors, they have three major advantages: motor torque generation is quick and accurate, a motor can be attached to each wheel, and motor torque can be estimated precisely. These advantages enable the realization of highperformance antilock braking and traction control systems, control of two-dimensional chassis motion, and estimation of road surface condition. In summary, we can achieve a large-scale development of future vehicles that employ three techniques: Electric Motors, Supercapacitors, and Wireless Power Transfer. This eliminates the requirement for engines, high performance Li-ion batteries, and large charging stations.