  The natural locomotion interface is critical to the development of many VR
applications. For household VR applications, there are two basic requirements:
natural immersive experience and minimized space occupation. The existing
locomotion strategies generally do not simultaneously satisfy these two
requirements well. This paper presents a novel omnidirectional treadmill (ODT)
system, named Hex-Core-MK1 (HCMK1). By implementing two kinds of mirror
symmetrical spiral rollers to generate the omnidirectional velocity field, this
proposed system is capable of providing real walking experiences with a
full-degree of freedom in an area as small as 1.76 m^2, while delivering great
advantages over several existing ODT systems in terms of weight, volume,
latency and dynamic performance. Compared with the sizes of Infinadeck and HCP,
the two best motor-driven ODTs so far, the 8 cm height of HCMK1 is only 20% of
Infinadeck and 50% of HCP. In addition, HCMK1 is a lightweight device weighing
only 110 kg, which provides possibilities of further expanding VR scenarios,
such as terrain simulation. The latency of HCMK1 is only 23ms. The experiments
show that HCMK1 can deliver on a starting acceleration of 16.00 m/s^2 and a
braking acceleration of 30.00 m/s^2.
