Hyundai Motor Co unveiled March 28, 2013, the "E4U" personal mobility vehicle at Seoul Motor Show 2013, which opens for the public from March 29 to April 7, 2013.
The E4U is a concept vehicle that can be actually driven and was designed by the company's Advanced Design Department. The initial letter "E" represents "egg," "evolution," "ecology," etc. It can be moved in any direction with a motor that rotates only in one direction.
Instead of tires, the vehicle uses a rotating semispherical part (like the lower half of a ball). When the part is vertical to the ground (with the apex of the semisphere touching the ground) and rotating in the horizontal direction, a force is generated to spin the vehicle.
To prevent the vehicle from spinning, it has two safety wheels on the rear side. At this point, the vehicle does not move even though the semispherical part is spinning because of the frictional force generated by the safety wheels. So, the wheels function like the tail rotor of a helicopter.
On the other hand, when the semispherical part is tilted, it becomes possible to move the vehicle because the rotative force is transmitted to the ground.
The semispherical part rotates counterclockwise. And the direction of travel can be controlled by using the feet placed on the part to tilt it.
To move forward, the left foot is used to tilt the semispherical part so that the left side of it contacts the ground and kicks the ground backward. As a result of its reaction force, the vehicle moves forward.
Likewise, when the right foot is used to tilt the semispherical part, the right side of it contacts the ground and kicks the ground forward, moving the vehicle backward. To turn right and left, the semispherical part needs to be tilted forward and backward, respectively.
According to a driver of the vehicle, it is necessary to get used to such operations. Without some practice, it does not move in the desired direction, the driver said.
The speed of the vehicle depends on the rotation speed of the motor and the angle of tilt. But, in a demonstration, its moving speed was as slow as that of a walking man. Hyundai started the development of the vehicle in October 2012 and showed it for the first time at the show.