On kinematic mechanism of a two-wheel skateboard: The essboard

In this paper, we investigate the kinematic mechanism and path planning of a two-caster nonholonomic vehicle (the Essboard) which is a recent variant of skateboards. Different from the most studied Snakeboard, the Essboard consists of a torsion bar and two platforms, each of which contains a pedal and a caster. We study the relationship between the tilt angle of the pedal and the wheel direction of the caster. This relationship clarifies how to control the wheel direction by adjusting the tilt angle. Furthermore, the rotational radius of the Essboard is derived for a given pair of tilt angles of both pedals. The rotational radius of the Essboard is much different to that of other skateboards. Two experiments are conducted to verify the results. These results clarify the kinematic mechanism and lay a solid foundation for further investigation of the Essboard.